@article{
author = {ArshadTorabi, Mohamad Amin and Danesh, Shahnaz and Tavakkolizadeh, Mohamadrez},
title = {The effect of municipal sewage sludge ash as replacement of cement on physical, mechanical and durability properties of concrete},
abstract ={Drict discharge of domestic wastewater(sewage) to the environment or into absorbing wells has caused many problems including surface and groundwater pollution. To reduce such problems, the number of wastewater treatment plants has increased significantly in Iran during the last two decades. During wastewater treatment, a significant amount of sludge, composed of organic and mineral material, is produced. This sludge, if not handled and disposed properly, can create serious environmental and health issues. One environmentally attractive way of dealing with such wastes is to use them in different types of applications. In this regard, many economical and beneficial methods have been developed to reuse sludge. Incineration of sludge for energy recovery or the use of sludge ash in cement-based construction materials are among these methods. Sludge incineration produces considerable amount of ash which should be disposed. However the ash can be used as cement substitude in procuction of cement-based material. The subject of using sludge ash as cement substitude has been investigated by a few researcher with the conclusion that the usage of ash can affect the final cement-based product quality. Based on their experimental results, the use of sludge ash tends to decrease the compressive strength of mortar or concrete. However, it should be mentioned that no research has yet been done to investigatethe the effects of sludge ash replacement on mechanical and durability properties of concrete. The main aim of this study was to investigate the effects of sludge ash usage as cement substitude on physical, mechanical and durability properties of concrete. For this purpose, the effects of three key parameters: replacement level ( 0-20%, by weight), curing times (7, 28, 91 and 180 days) and water-cementitious material ratio (0.35, 0.45 and 0.55) were investigated. The sludge used in this research was obtained from one of the local wastewater treatment plants, which subsequently was dried and then was incinerated at 800oC to produce ash, The ash was in general, made up of irregular grains which were aggregates of smaller particles. Also, the ash was composed mainly of calcium, silica and aluminium oxides. The results showed that increasing the amount of sludge ash induced higher mortar setting times as compared to the control samples, using Vicat test. The effect of ash content on mechanical properties of concrete samples was carried out by compressive strength tests. Results indicated that for 7 and 28 days curing time, concrete samples containing a mixture of sludge ash and cement yielded lower compressive strength values than those samples using only cement (without any ash content). However, for curing times greater than 28 days, the increase in ash content of concrete samples (0-15% by weight) led to an increase in compressive strength. Water absorption and electrical resistivity tests were conducted to determine the durability of concrete containing sewage sludge ash. As blending percentages of ash content increased fom 5% to 20%, electrical resistivity of concrete samples decreased for regardless of the applied curing times. This phenomenon might be the result of increased porosity and material ionization.},
Keywords = {Municipal sewage sludge ash,concrete,compressive strength,durability,Water Absorption},
volume = {17},
Number = {1},
pages = {1-12},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9041-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9041-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {---------------------------------------------},
abstract ={--------------------------------------------},
Keywords = {},
volume = {17},
Number = {1},
pages = {1-265},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5191-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5191-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {1, 1 and F, A},
title = {Comparision of stress variables performance in predicting the shear strength of unsaturated soils},
abstract ={Shear strength is one of the most important features in mechanical behavior of soils. The shear strength of unsaturated soils is still a controversial discussion between the researchers in this field. The methods of determining unsaturated shear strength are classified into two major categories; one of them employs two independent stress variables namely matric suction and net stress and saturated and unsaturated strength parameters are considered to be independent. In other words, as soon as the pore water pressure becomes negative, the saturated effective friction angle and cohesion become invalid. This approach became dominant especially since the validity of effective stress in unsaturated soils was questioned because it was not clear how to describe the collapse phenomenon through effective stress concept. In late 90’s some researchers referred back to effective stress concept and some ambiguity in explaining collapse was resolved. In this approach, effective stress is the main stress variable. Net stress and suction are combined into effective stress. The saturated and unsaturated shear strength parameters are assumed are not assumed to be independent from each other and there is a smooth transition between saturated and unsaturated soil modeling. In this research these two approaches are compared by means of unsaturated direct shear experiments and some relevant experimental data from literature. The advantages and shortcomings of the mentioned methods are analyzed. In the direct shear experiments, a wide range of soil suction was applied to the samples. Therefore it is possible to compare the effective stress and independent stress approaches in a wide range of suctions. The suctions of samples were measured by filter paper method. By plotting the failure envelopes in two approaches, the advantage of effective stress approach over the approach of independent stress variables is obvious. This advantage is especially drastic at higher suctions. The experimental data from literature similarly revealed this result. Thus it can be stated that effective stress approach is simpler and less time consuming since the failure envelope is a unique line for all suctions and strength parameters of a soil at saturated and unsaturated states are identical. On the contrary of independent stress variable approach, it is not required to measure strength parameters at various suctions. In the other words, if the effective stress is properly estimated, the unsaturated shear strength can be predicted straightforwardly. Effective stress parameter is the key factor for appropriate evaluation of effective stress in unsaturated soils. One of the highly cited proposed equations for effective stress parameter is verified by experimental data. The values of predicted effective stress parameter and the values measured from experiment are plotted versus suction. There is a good agreement between the effective stress parameters calculated from the equation and those measured from experimental data. Therefore it can be concluded that the empirical equation can accurately predict the effective stress parameter. It is worth mentioning that by normalizing the suction through dividing it into air entry suction, the effective stress parameter versus normalized suction becomes a unique line regardless of soil type. Thus the effect of soil type and its structure is normalized by means of using suction ratio.},
Keywords = {Shear Strength,Suction,Effective stress,Unsaturated},
volume = {17},
Number = {1},
pages = {13-27},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1178-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1178-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Beheshti-Aval, Seyed Bahram},
title = {Multi-Level Behavior Factors for Steel Moment Frame Accompanied with RC Slit Shear Wall System},
abstract ={Earthquake loads induce significant damages and cause widespread failures into buildings. Having appropriate system against seismic loads is a minimum necessary requirement for a structure. Moment Resisting Frame Systems (MRFS) are one of the common seismic resisting systems against lateral seismic loads. Ductility is the most important properties of these kinds of systems; but increase in ductility leads to decrease stiffness and increase lateral deflections and hence induces damages to nonstructural components. Although stiffness can be magnified through increasing section sizes of members, but it would not be economical. To compensate this deficiency, the combination of these systems with reinforced concrete (RC) shear walls may be useful. Although in general, this combination (RC shear walls and MRFS) decreases the section size and increase stiffness; but in low rise structures using this combined system cause decrease in ductility and dissipation of energy under moderate/strong earthquakes.This deficiency can be improved by using vertical slits in RC shear walls of low to moderate height. These slits invert shear behavior of RC shear wall into flexural behavior of several columns and are able to increase ductility. So, for the first time in this paper, a study was conducted on introducing behavior factor (R) for Steel Moment Frame (SMF) with reinforced concrete slit shear wall system at two levels of demand and supply. In view of existing concerns about precise of behavior factors in seismic design codes, due to developing these factors based on engineering judgment from observing seismic performance of structures subjected to past earthquakes besides the lake of these information in current seismic design codes causes the seismic design of RC slit shear wall system needs more research works. The behavior factors are used to reduce the linear elastic design spectrum to account for the energy dissipation capacity, over-strength and redundancy of the structure. The most distinctive feature of this study respecting to similar studies is multi-level definition of behavior factors and their extraction with respect to seismic intensity, and accepted damage level as expected performance levels in designing RC slit shear wall structural system. Hence, the demand/supply behavior factors are determined with a more accurate attitude involving the effective parameters such as ductility, over-strength, redundancy, seismic hazard level, performance levels, etc. In this study, to determine the appropriate behavior factor, static pushover analysis along with Incremental Dynamic Analysis (IDA), are used. The behavior factors in two levels of demand and supply are obtained with two procedures: At the first, the pushover analysis was applied on case study structures and then relationship for SDOF system of Newmark and Hall, Nassar and Krawinkler, and Miranda to evaluate behavior factor for MDOF structures were used. At the second stage both pushover and incremental dynamic analysis were used to achieve directly the behavior factor for MDOF structures. In this paper, two 5 and 10-story steel moment resisting frame with RC slit and ordinary shear wall systems were designed by ETABS software. These structures were designed in which their behavior factors were the same values. Then the pushover and IDA were conducted on sample structures using nonlinear analysis software PERFORM. Results show that, although initial elastic stiffness has not been considerably changed in slit RC shear wall systems, but they show higher behavior factor relative to regular RC shear wall systems. Converting the shear behavior of RC ordinary shear wall to ductile flexural behavior of a series of wall pieces as columns by providing slits in shear wall may be considered as the reason for achieving more ductility and dissipating high seismic energy in this innovative systems.},
Keywords = {steel moment frame,reinforced concrete slit wall,behavior factor,pushover analysis,Incremental dynamic analysis},
volume = {17},
Number = {1},
pages = {29-42},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11617-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11617-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Tasnimi, Abbas},
title = {Assessment of the Park- Ang Damage Index for Performance Levels of RC Moment Resisting Frames},
abstract ={The main goal of seismic design is having safety while earthquake happens and making a structure repairable. For estimating the damages in the elements criterions are defined as damage indices. Damage indices are functions consist of some damage variables and show the effect of those variables on the element’s damage. One of the most important damage indices is the Park-Ang damage index. It shows the damage of reinforced concrete elements as a linear combination of maximum deformations and absorbed cyclic energy. The analytical value of this damage index for the state of not having any damage will zero and for the collapse of the element should be equal one. The Park-Ang damage index has a non-negative factor shows the reduction of element’s resistance in cyclic loading and specifies the energy dissipation and the strength damage of the elements. This factor has been used for calibrating damage index and it has been found that the damage index is merged to one in the failure point. Applying this model in structural systems requires determination of an overall member’s deformation. Since inelastic behavior is limited to plastic zones adjacent to the ends of a member it is difficult to correlate, the relationship between overall member deformation, local plastic rotations and the damage index. So a modified version of this model developed by Kunnath and et al. The most important difference between Kunnath model and Park-Ang model is representing this equation based on the moment-curvature diagram and replacing the non-dimensional factor with the strength deterioration factor in a hysteretic model. Supposing this factor as a constant will increase the diversion of the damage index in collapse prevention performance level. In this paper, the Park-Ang damage index and its correctional relations for the various performance levels which contain immediate occupancy, life safety and the collapse prevention level has been evaluated and the values of damage index at these levels has been specified. For this purpose, three reinforced concrete frames with various numbers of stories have been designed for three levels of performances have been used for this purpose. Nonlinear dynamic analysis has been done with seven earthquake acceleration records and finally the damage analysis has been done for them. The damage index has been derived for all of these nine frames and the values of damage indices have been evaluated. The beam damage indices are related directly to the rotation which happens in the plastic hinges. In components with immediate occupancy level, this linear characteistic is more clear but with increasing the rotation in the componenets or in the collapse prevention level, damage indices will more diverge. In this paper, it has been shown that this damage index needs to be investigated furtherer at the collapse prevention level and the second part of the damage index (strength damage) shall be determined by the element’s type and level of performance. The sensitivity of damage index is little to the column damages and the damage caused by the weak story is low and needs to be evaluated.},
Keywords = {Damage Index,Performance levels,RC Moment Resisting Frames,Seismic Performance},
volume = {17},
Number = {1},
pages = {43-53},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9414-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9414-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Tarinejad, Reza and Pourgholi, Mehran and Yaghmaei-Sabegh, Sam},
title = {System Identification of Arch Dams Using Balanced Stochastic Subspace Identification},
abstract ={Finite element model is the conventional method used for static and dynamic analysis of widely used structures such as dams and bridges, since it is cheap and requires no special tools. Nevertheless, these models are not able to describe the accurate behavior of structures against dynamic loads because of simplifying assumptions used in numerical modeling process, including loading, boundary conditions and flexibility. Nowadays, modal testing is used to solve these problems. The dynamic tests used to identify civil structures’ system usually include forced, free and environment vibration tests. Considering either unknown nature of inputs or failure to measure them, some methods have been developed to analyze the results of dynamic tests which are based on measuring only output data and are known as operational modal analysis. Some of such methods are Peak Picking (PP), Frequency Domain Decomposition (FDD) and stochastic subspace methods. However, unknown nature of applied forces, the presence of environmental noise and measurement errors contribute to some uncertainties within the results of these tests. In this article, a modal analysis is presented within a stochastic subspace which is among the most robust and accurate system identification techniques. In contrast to the previous methodologies, this analysis identifies dynamic properties in optimized space instead of data space by extracting ortho-normal vector of data space. Given the optimum nature of the proposed method, more accuracy in detection and removal of unstable poles as well as high-speed analysis can be served as its advantages. In order to evaluate the proposed method in terms of civil systems detection, seismic data (being among the most real and strong environmental vibrations) and steady-state sinusoidal excitation (which is among the most precise forced vibration tests) were used. In the first step, 2001 San Fernando earthquake data were analyzed using SSI-CCA and SSI-data methods, the results of which are presented in the following. Data processing rate in the SSI-CCA method is almost twice that in SSI-data method which is because of processing in an optimum space while lowering the use of least squares method to compute system vector. Furthermore, there is one unstable pole in the results of the proposed method while 4 noisy characteristics were recognized in the results of SSI-Data method. Estimated damping ratios comprised the major difference observed in this analysis using above-mentioned two methods. Modal damping ratios estimated by the proposed method were 60% closer to the previous results when compared to those of the previous subspace method. Mode shapes of both subspace methods with MAC value of 92% and 75% for the first and the second modes, respectively, are well correlated with each other. Due to lack of access to the mode shape vectors of Alves’s method, it was not feasible to calculate the corresponding MAC value. In the following, forced vibration test results of Rajai Dam conducted by steady sine excitation in 2000 and analyzed by a method known as four spectral, are re-processed Using the SSI-CCA method. As results indicate, using the proposed method the first three modes are obtained that were not on the preliminary results. In addition, other modes are of great fit with the values of the finite element.},
Keywords = {Hankel Matric,Canonical Correlation Analysis,Stochastic Subspace},
volume = {17},
Number = {1},
pages = {53-64},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9909-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9909-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Nasiri, Masou},
title = {Experimental Studies of Cohesion Effect on Earth Slope Reinforced using stone column},
abstract ={The increasing demand for engineered cut and fill slopes on construction goals has increased the need of understanding of analytical methods, investigation tools and the most important stabilization methods to solve slope stability problems. The first step to maintain the stability of an earth slope is performing excavation in the slope crest or/and filling in the slope toe. This is the cheapest way (model) for stabilization of earth slopes. If the model cannot provide the required factor of safety, it is necessary to use other stabilization methods. Numerical and laboratory methods are useful for modeling earth slopes stabilization. Modeling the stability of earth slopes using numerical methods is a common practice in geotechnical engineering. Moreover , stabilization of earth slopes using piles has been practiced by many researchers by using numerical and analytical methods. Application of numerical and analytical methods to stabilization of earth slopes using piles is an issue commonly discussed by various researchers. Although , numerical and analytical methods have special capabilities, laboratory modeling is more reliable. Stability slope analysis has attract lots of researchers attention all across the world and it shows the significance of this matter. When we are suspicious about stability of earth slopes, immediate actions and preventative steps should be used for suppression of instability occurrence. Many projects intersect in valleys and rides , which can be prone to slope stability problems. Natural slopes that have been stable for many years may suddenly fail because of many reasons, therefore finding useful techniques for these matters now days are a great concern for geotechnical engineers. In all earth slopes the primary way for stabilization is the excavation in slope crest and/or filling slope toes , if this action would not increase safety factor enough , other procedures should be applied. Three common styles of stabilization methods are ; vertical reinforcement (such as stone columns and piles) , horizontal reinforcement (like Geo - grids) , oblique reinforcement (such as nailing). Stability of natural slopes is one of important issues in Geotechnical engineering. using easy and economical methods for improving stability of slopes are one of the greatest challenges that face engineers. One of the common methods that is use for increasing the safety factor of slopes is stone columns. All of the experimental tests were modeled and compared using the limit equilibrium (LE) and finite element (FE) methods, which are compliant with each other. Understanding of soil property is crucial for analysis of earth slopes, in this study effect of cohesion in embankment is considered, and based on exact understanding of this property and performing laboratory modeling and by using finite element method software (PLAXIS2D) and finite difference method software (FLAC3D), results are achieved. The sand slope is saturated through precipitation and failure after loading by installing the stone column at the middle of slope. Experimental studies in this article have the potential to give valuable information about effects of embankment cohesion and penetration depth of stone column into the stiffer layer, in stability of stone column reinforced earth slopes.},
Keywords = {Earth Slope,Stone Column,Cohesion,Stabilization},
volume = {17},
Number = {1},
pages = {65-78},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12324-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12324-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Ayyoubzadeh, Seyed Ali and Saneie, Mojtaba and Hassanzadeh, Mehdi},
title = {Experimental study of the effect of side weir on lateral variation of bedform dimensions in main channel},
abstract ={Side weir is one of the most important structures in flood treatment projects that are designed provided the main channel bed is rigid. However, in the most practical channels, the main channel bed is movable and the changes in bed can produce wavelike patterns known as bed forms and another additional effect of side weir on bed forms is that it causes an aggradation of sediment particles in front of itself. These two products of using side weir in movable beds cause an additional bed resistance in comparison with the state that there isn’t any weir on sidewall of main channel and so the flow level with using side weir will rise subsequently and this means more diversion ratio. Thus, In order to study the effect of side weir hydraulic and geometric properties through Froude Numbers, diversion discharge ratios and flow depths on bed forms and its effect on design conditions, the present research work is carried out. A set of 9 experiments were conducted in a flume with dimensions of 0.85 m width, 0.40 m height and 10 m length on a mobile bed having median sediment particle size of 0.23 mm running with side weirs of crest lengths of 20, 40 and 60 cm . In addition a set of 3 experiments without using a weir were considered as bench mark experiments for comparison purposes. After running a determined flow in flume regarding with the bed profiles should reach a balance it was stopped after 1-3 hours. The bed topography at the end of each experimental run was recorded using automatic bed profiler in a length of 220 cm of main channel. This topography was recorded in a net of points that were distributed in a distance of 5 cm in length and 3 cm in width. The dimensions of bed forms were then determined using the well-known crest-through method. The results indicated that the effect of flow depth, discharge, and diversion ratio on bed form dimensions are significant and increasing these parameters cause an increasing influence on bed form dimensions. In this study 4 equations are suggested that both of them are for bench mark experiments and two others are for main experiment. The coefficients of these relations were determined by Solver Add In program in Excel with using 80 percent of data that were selected in chance and then they were verified with using remaining 20 percent of data. Verification of relations also illustrated that for both length and width of bed form in main experiments the maximum error of related equations is 50 percent and maximum error of relations for bench mark experiments is 30 percent. Analyzing these relations revealed an important influence of applying side weirs on lateral variation of bed form dimensions in the main channel so that it is indicated that bed form length and height near side weir will increase up to 70 and 2 percent of channel width, respectively, in comparison with the experiments that side weir is not used.},
Keywords = {Side weir,bed form dimensions,Experimental study,Froude Number effect,diversion ratio},
volume = {17},
Number = {1},
pages = {79-88},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8401-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8401-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Free Vibration of Beam-Like Structures Resting on a Pasternak Elastic Foundation},
abstract ={The beam theory is used in the analysis and design of a wide range of structures, from buildings to bridges to the load-bearing bones of the human body. Beams resting on elastic foundation have wide application in many branches of engineering problems namely geotechnics, road, railroad and marine engineering and bio-mechanics. The foundation is very often a rather complex medium; e.g., a rubberlike fuel binder, snow, or granular soil. The key issue in the analysis is modelling the contact between the structural elements and the elastic bed. Since of interest here is the response of the foundation at the contact area and not the stresses or displacements inside the foundation material, In most cases the contact is presented by replacing the elastic foundation with simple models, usually spring elements. The most frequently used foundation model in the analysis of beam on elastic foundation problems is the Winkler foundation model. In the Winkler model, the elastic bed is modeled as uniformly distributed, mutually independent, and linear elastic vertical springs which produce distributed reactions in the direction of the deflection of the beam. However since the model does not take into account either continuity or cohesion of the bed, it may be considered as a rather crude representation of the elastic foundation. In order to find a physically close and mathematically simple foundation model, Pasternak proposed a so-called two-parameter foundation model with shear interactions. The first foundation parameter is the same as the Winkler foundation model and the second one is the stiffness of the shearing layer in the Pasternak foundation model. Dynamic analysis is an important part of structural investigation and the results of free vibration analysis are useful in this context. Vibration problems of beams on elastic foundation occupy an important place in many fields of structural and foundation engineering.With the increase of thickness, existence of simplifying hypotheses in beam theories such as the ignorance of rotational inertial and transverse shear deformation in classic theory, application of determination coefficient in first-order shear theory and expression of one or few unknown functions based on other functions in higher-order shear theories is accompanied by reduction in accuracy of these theories. This represents the necessity of precise and analytical solutions for beam problems with the least number of simplifying hypotheses and for different thicknesses. In the present study, the analytical solution for the problem of free vibration of homogeneous prismatic simply supported beam with rectangular solid sections and desired thickness resting on Pasternak elastic foundation is provided for completely isotropic behaviors under two-dimensional theory of elasticity and functions of displacement potentials. Characteristic equations of natural vibration are defined by solving one partial differential equations of fourth order through separation of variables and application of boundary conditions. The major characteristics of present study are lack of limitation of thickness and its validity for beams of low, medium and large thickness. To verify, the results of present study were compared with those of other studies. The results show that increases of foundation parameters is associated with an increased natural frequency, The intensity by increasing the ratio of thickness to length and in values larger than 0.2 and in the higher modes of vibration is reduced considerably.},
Keywords = {Natural Frequency,Free vibration,Deep Beam,elastic foundation,Potential Functions},
volume = {17},
Number = {1},
pages = {89-101},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-2326-en.html},
eprint = {http://journals.modares.ac.ir/article-16-2326-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Application of Reinforcement Concrete Layer Method for Retrofit of Slant Jack Arch Roofs in Masonary Buidlings},
abstract ={Jack arch masonry slab, developed in the 19th century in Britain has been used widely to floor and roof industrial and residential masonry buildings in many parts of the world. It is still in use in parts of Europe, the Middle East and Indian subcontinent. Taking into consideration the widespread use of the jack arch flooring and its ease of constructing compared to the more modern concrete-based slabs, it is rather surprising that there is no mention of the system in codes of practical installation . Most of these roofs are built in traditional ways and little control is applied on their method of construction. Collapse of a large number of these composite slabs during past earthquakes pointed out the weakness of this type of flooring to seismic loading. It has also highlighted the need for developing appropriate retrofitting schemes sience Statistics has showed that over half of the slabs used in buildings in Iran are jack arch roofs. The point is that these slabs (specially the slant type that is widely used in buildings of northern area in Iran) do not show appropriate seismic performance in severe earthquakes. Therefore rehabilitation of them needs to be considered. One of the effective methods is to add a thin layer of reinforced concrete over the slab. The retrofitting procedure includes; removing the slab flooring finish, then placing over the slab a mesh of reinforcement bars and finally covering the mesh with a thin layer of concrete. The effectiveness of such a method needs more investigations. To further investigate the seismic behavior of these roofs, response modification factor can be utilized as a well-known seismic parameter. This study investigates the seismic performance of masonry buildings with slant jack arch slabs retrofitted by the method of adding a layer of reinforcement concrete. Two groups of one story masonry buildings with jack arch masonry slabs are designed including roofs with slopes of 0, 10, 15 and 20 degrees with and without concrete layer for roof retrofitting. Static nonlinear (pushover) analysis is carried out. Nonlinear analysis program “ANSYS” is employed for the analyses. The load–displacement curves for both types of models are obtained and variations of strength, ductility factor, stiffness and rigidity of roofs n both types of models are investigated. Response modification factor of two groups are calculated and results are compared. Results show that according to standard no. 2800 criterion, slant jack arch masonry slabs are classified as semi-rigid roofs and by retrofitting them, their rigidity can be enhanced. Increasing the Slope of roofs inversely affects the Response modification factor (R), strength and elastic stiffness of structure. Finally For the consideration of economics factors, a cost analysis based on the tariffs of the Iranian Management and Programming Organization is carried out on three conventional methods of roof retrofitting (method of adding a concrete layer on the roof, steel grid method and tie-bracing method recommended by standard no. 2800). The obtained results indicate that method of adding a concrete layer is the most cost-effective method for jack arch retrofitting.},
Keywords = {masonry buildings,jack arch roof,slant roof,Concrete Layer,Seismic evaluation},
volume = {17},
Number = {1},
pages = {102-114},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-2716-en.html},
eprint = {http://journals.modares.ac.ir/article-16-2716-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Siahpolo, Navi},
title = {On the Effect of Near and Far Field Earthquakes on Strength Reduction Factor and Inelastic to Elastic Displacement Ratio, Demand Ductility Concept},
abstract ={The experience of previous earthquakes shows that the inelastic response of structure relates to the intensity and content of ground motion. In this case, the evaluation of nonlinear response of structure demonstrates the reduction in the base shear force. This reduction leads to inelastic base shear is defined by Behavior Factor (strength reduction factor) in seismic codes. One of the important parts in R factor is ductility reduction factor Rμ or. While Rμ is related to type of earthquake, it seems that for near fault motions there would be a different value in comparison to ordinary earthquakes. Fir the near fault earthquakes, due to direction of fault rupture from the site, the directivity effect becomes an important parameter. Previous researches show that for forward directivity effect, there would be two components for earthquakes. One is strike normal and the other is strike parallel. In this paper these components are named as the SN and SP. Also, in concept of performance -based design, to calculate target displacement, the ratio between inelastic and elastic response of structure is an important index. In this paper, this ratio is named as CR. It is good to mention that CR factor is defined as a C1 coefficient in FEMA440. In the previous research, the evaluation of CR for near and far fault motions has less considered. To evaluate Rμ and CR, the extended number of SDOF systems (from 0.2 to 4 Sec.) for four levels of target ductility (2, 3, 4 and 5) have been considered. Then, Rμ and CR calculated for near field (normal and parallel component) and far fault earthquakes. At the end, for the strike normal component, a sensitivity analysis was carried out due to strain hardening ratio and inherent damping. To perform the analysis in Opensees, the nonlinear time history analysis was selected. During the assessment of Rμ and CR, the strain hardening slope and damping have been selected 3% and 5% respectively. The steel material was defined as bilinear. To set the demand ductility with prescribed target ductility, during trial and error procedure, the yield strength of SDOF was changed since the target ductility achieved. To evaluate sensitivity of Rμ and CR to the effect of strain hardening slope, this factor was selected as 0, 3, 5 and 10%. In the case of damping sensitivity, inherent damping were selected as 2, 5. 10 and 20%. To solve the inelastic equation of motion, the Newmark-Beta method was selected. The inelasticity in Opensees was modeled with distributed plasticity using the fiber element. Finally to calculate Rμ and CR for near and far field motions, approximately 84000 nonlinear time history analysis have been carried out. Also, to study sensitivity of Rμ and CR to damping and strain hardening ratio for the strike normal earthquake, approximately 22400 nonlinear time history analysis have been carried out. The results show that for all three sets of the earthquake, the Rμ increases and then constant while the fundamental period (T) increases. For small value of ductility (μ), increasing T may lead that Rμ converges to target ductility. In the near field, while T and μ increase, Rμ is almost greater than μ. Also, for small value of T, Rμ is not depend on demand μ. The study shows using far field value of Rμ for near field motions may lead to Non-conservative value. Furthermore, while T increases, the CR value converges to the unit. In the short period, CR depends on μ and T severely. Using CR of far field against SN component leads to Non-conservative result. For a constant value of μ and T, increasing damping increases CR. Using C1 for near field motions is Non-conservative for near field motions. Also, for short periods and high ductility demand, CR, corresponding to SN component is 40% greater than C1. Evaluation of ratio between displacement modification factor and behavior factor shows (Cd/R) for T greater than 1 Sec. this ratio converges to the unit. For small period value, this ratio is dependent to period significantly. Also, using Cd/R of far field for near field motions may lead to inaccurate results.},
Keywords = {Near field motions,ductility,Nonlinear time history analysis,behavior factor,FEMA440},
volume = {17},
Number = {1},
pages = {115-127},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-10648-en.html},
eprint = {http://journals.modares.ac.ir/article-16-10648-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Taherkhani, Hasan and JalaliJirandehi, Masou},
title = {Investigation of Top-Down Cracking in Asphalt Pavements Using FEM},
abstract ={Top-down cracking (TDC) is among the major forms of asphaltic pavement distresses that significantly affects the serviceability and development of structural failure. Interaction of tire and pavement interaction plays a key role in the initiation of TDC. This study utilizes viscoelastic analysis using finite element modeling to evaluate the influence of axle loads and tire types on the top down cracking in asphaltic pavements. The effect of three axle loads of 5, 8.2 and 15 ton and two tire configurations (conventional dual tire assembly and super single tire) on TDC in Geogrid reinforced and unreinforced pavements has been investigated. The results show that under axle load of 5 and 8.2 ton top down cracking occurs, initialy at the inner edges of the tires, while under axle load of 15 ton its occurence between the tires is sooner than the other zones. Among bottom-up cracking (BUC) and TDC, BUC is more sensitive to the variations of tire type. The study also indicates that the reinforcement of pavement using geogrid at the bottom of asphalt layer is more effective on the bottom up cracking than on the top down cracking. By comparison, the super single tire was shown to create more TDC damage ratio than the dual tires assembly in both reinforced and unreinforced pavements. Top-down cracking (TDC) is among the major forms of asphaltic pavement distresses that significantly affects the serviceability and development of structural failure. Interaction of tire and pavement interaction plays a key role in the initiation of TDC. This study utilizes viscoelastic analysis using finite element modeling to evaluate the influence of axle loads and tire types on the top down cracking in asphaltic pavements. The effect of three axle loads of 5, 8.2 and 15 ton and two tire configurations (conventional dual tire assembly and super single tire) on TDC in Geogrid reinforced and unreinforced pavements has been investigated. The results show that under axle load of 5 and 8.2 ton top down cracking occurs, initialy at the inner edges of the tires, while under axle load of 15 ton its occurence between the tires is sooner than the other zones. Among bottom-up cracking (BUC) and TDC, BUC is more sensitive to the variations of tire type. The study also indicates that the reinforcement of pavement using geogrid at the bottom of asphalt layer is more effective on the bottom up cracking than on the top down cracking. By comparison, the super single tire was shown to create more TDC damage ratio than the dual tires assembly in both reinforced and unreinforced pavements. Top-down cracking (TDC) is among the major forms of asphaltic pavement distresses that significantly affects the serviceability and development of structural failure. Interaction of tire and pavement interaction plays a key role in the initiation of TDC. This study utilizes viscoelastic analysis using finite element modeling to evaluate the influence of axle loads and tire types on the top down cracking in asphaltic pavements. The effect of three axle loads of 5, 8.2 and 15 ton and two tire configurations (conventional dual tire assembly and super single tire) on TDC in Geogrid reinforced and unreinforced pavements has been investigated. The results show that under axle load of 5 and 8.2 ton top down cracking occurs, initialy at the inner edges of the tires, while under axle load of 15 ton its occurence between the tires is sooner than the other zones. Among bottom-up cracking (BUC) and TDC, BUC is more sensitive to the variations of tire type. The study also indicates that the reinforcement of pavement using geogrid at the bottom of asphalt layer is more effective on the bottom up cracking than on the top down cracking. By comparison, the super single tire was shown to create more TDC damage ratio than the dual tires assembly in both reinforced and unreinforced pavements.},
Keywords = {Asphalt Pavement,Top-Down Cracking,Axle Weight,Tire Type,Geogrid},
volume = {17},
Number = {1},
pages = {127-135},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4335-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4335-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Evaluation of Stripping in Asphalt Concrete Pavement by Experimental Methods},
abstract ={Adhesion of bitumen to Aggregates is the basis of the strength of the asphalt pavements. The term "stripping" is used for hot mix asphalt (HMA) mixtures to show the separation of asphalt binder film from aggregate surfaces, due primarily to the action of moisture and/or vapor. If this phenomenon is eliminated for any reason, stripping will be occurred. This problem not only is as a distinct distress but also can cause other asphalt distresses which are finally resulted in the overthrow of road. Mainly because this distress either results from or is dominated by moisture, it is usually called “moisture damage” or “moisture susceptibility”. The main goal in this research is to study stripping in asphalt mixtures. The key factors which must be considered in this research are aggregates and selecting the suitable approach for controlling and assessment of this distress in laboratory conditions. the most recent approach introduced is the rehabilitation and modification of asphalt mixtures against stripping, whether asphalt concrete or surface treatment. Thus, in this study on "Zanjan-Qazvin" freeway where this distress have usually been observed, the aggregates for constructing the asphalt was selected from sections of the aggregate the stripping intensity of which is higher than the others. First, the sensitivity of stripping was specified by XRF & XRD analysis. There is a requisite to do a realistic laboratory test method to predict moisture susceptibility of HMA mixtures. It was observed in the case histories that the asphalt pavements were saturated with water (55-80% saturated as specified in ASTM D4867 or AASHTO T283). Thereafter, in order to calculate the tensile strength ratio, it is required to consider unsaturated specimens some of which remained with no conditions. A laboratory test procedure that simulates such conditions will be more realistic. The cylindrical asphalt concrete specimens are constructed by marshal method. Thus, their durability is evaluated according to AASHTO-T283. In this method, those stabilities are measured by indirect tensile test; the amount of their stripping was previously estimated by boiling test. Results showed that according to literature boiling test method is not reliable enough to be accurate. On the other hand, the result of laboratory test of AASHTO-T283 is quantitative and much more technical. Also, using hydrated lime 3% for this material can be useful to reduce the adverse effect of stripping, and it can be used as a suitable anti-stripping. Based on the probabilistic analysis, all the specimens result either in Indirect Tensile Test, or in the TSR results. This showed the improvement of the strength. Also, the rate of increasing is close to that of the parabolic curve. WTAT test was carried out over the surface treatment specimens constructed using these aggregates. Hydrated lime was utilized as the most important anti-stripping additive for prevention and rehabilitation of this distress in all of the experiments. },
Keywords = {Key Words: Stripping,Moisture Damage,Asphalt Pavement,Anti-stripping Additives,And Hydrated Lime},
volume = {17},
Number = {1},
pages = {135-144},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12033-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12033-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Eghbalzadeh, Afshin and AZIMI, HAMED and JAVAN, MITRA},
title = {The upstream Froude number effect on the flow field of the U-shaped channel along the side weir in the supercritical flow regimes},
abstract ={The U-shaped channels are applied as transition cross-section from rectangular to circular in manholes. Also the U-shaped channels along the side weirs are used in the sewage networks, irrigation-drainage systems, flood protection and etc. The flow in the main channel along the side weir can be the supercritical conditions. In this study, the free surface flow in the supercritical regime has been simulated by FLOW-3D software, RNG model and volume of fluid (VOF) scheme in a U-shaped channel along the side weir. The comparison between the numerical and experimental results showed that the numerical simulation predicted the free surface flow with the reasonable accuracy. Generally, the flow depth decreases with distance from the upstream end of the side weir towards the downstream end in the U-shaped channel. The APE and RMSE of the water surface profile along the side weir have been computed 1.7% and 0.213%, respectively. Also, the APE and RMSE were respectively 3.8% and 0.0177% for the discharges over the side weir. In continue, the effects of the upstream Froude number on the flow pattern in the main channel were investigated. For all Froude numbers, because of entrance effects, a free surface drop occurred at the upstream end of the side weir and the water depth gradually reduced toward the downstream end. Then, a surface jump happened at the last fourth of the side weir length in vicinity of the inner bank. Unlike the potential energy, the kinetic energy increases along the surface jump. Also, a stagnation point is created at the end of the surface jump. The height of this stagnation point increases with increasing the Froude numbers. In addition, the dividing stream surface and stagnation zone were respectively produced near the inner and outer bank in the main channel along a side weir. The dividing stream surface reduces from channel bottom toward the side weir crest then increases to the flow surface. Also, the dimensions of the dividing stream surface and stagnation zone increased with increasing Froude number. The maximum lateral flow in the U-shaped channel occurs almost at the downstream end of the side weir. The transverse velocity increases at each cross-section of the main channel with increasing Froude number. The angle of the spilling jet was close to 90° at the upstream and downstream of the side weir crest and the pattern of spilling jet angle is similar for all Froude numbers. The minimum angle of the spilling happens approximately at the downstream of the side weir crest however, the minimum decreases with increasing Froude number. The pattern of the bed shear stress can be used to prediction of the areas of the scour and sedimentation in the alluvial channels. In the U-shaped channel along a side weir, the bed shear stress increases along the main channel axis form the beginning of the side weir toward the middle then decreases toward the downstream end. Generally, with increasing Froude number, the bed shear stress increases in the main channel along the side weir.},
Keywords = {Supercritical flow,U-shaped channel,Side weir,numerical simulation,Froude number},
volume = {17},
Number = {1},
pages = {145-157},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11993-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11993-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Abolbashari, Mohammad Hossei},
title = {Optimization of Nonlinear Structures Using Evolutionary Structural Optimization (ESO)},
abstract ={Evolutionary structural optimization (ESO) is based on the simple concept of systematically removing inefficient material from the structure after each finite element analysis, so that the resulting design is gradually evolved to an optimum. The bidirectional evolutionary structural optimization (BESO) method is a new version of the ESO method in which simultaneously removing and adding elements is allowed. Due to the importance of nonlinear structural analysis, in this study the BESO approach is used for nonlinear analysis of structures. The problems nonlinearity is assumed for the geometry, for the material, and for both geometry and material. In the first example, the BESO is applied to maximize the stiffness of a cantilever beam with a time dependent loading. Next, the BESO is applied to optimize the stiffness of a plate with the material nonlinearity. The results show that the nonlinear analysis leads to a much stiffer design. In the third example, a cantilever beam with both material and geometry nonlinearity is considered. The beam is also to be optimized for stiffness. The optimized shapes are compared for linear and nonlinear analysis against the SIMP. Furthermore, effectiveness of the ESO is proved by applying them to some shape optimization problems. The aim is to find the best fillet and notch shape so that it possesses a lower stress concentration factor. Design boundary has been set with some control points and optimization process is only applied to these points. First a square plate with a circular hole at its center is optimized for minimizing the stress concentration. The obtained results for linear and nonlinear analysis using ESO are compared with the results obtained using the biological growth method. Then, a square plate with a rhombus hole is optimized for stress concentration. It is concluded that using ESO, the maximum stress concentration around the boundary of the hole can be significantly decreased with linear analysis and the ESO is a powerful alternative for the biological growth method. The ESO method is finally used for shape optimization of geometrically different fillet for minimization the stress concentration. The material is assumed nonlinear while there is geometrical nonlinearity for loading. The results are compared with that of Wu who has used the fully stressed design criterion. The results show that using the ESO, the stress concentration factor is significantly redused and in this case it is reduced by 22%. In this way, the optimum shapes have completely uniform stress in the boundary of the fillet. The results show that the ESO has a superior capability for shape optimization of fillets of nonlinear structures and in this case the maximum stress is reduced by 7.7%. Furthermore, effectiveness of the ESO is proved by applying them to some shape optimization problems. The aim is to find the best fillet and notch shape so that it possesses a lower stress concentration factor. Design boundary has been set with some control points and optimization process is only applied to these points. First a square plate with a circular hole at its center is optimized for minimizing the stress concentration. The obtained results for linear and nonlinear analysis using ESO are compared with the results obtained using the biological growth method. Then, a square plate with a rhombus hole is optimized for stress concentration. It is concluded that using ESO, the maximum stress concentration around the boundary of the hole can be significantly decreased with linear analysis and the ESO is a powerful alternative for the biological growth method. The ESO method is finally used for shape optimization of geometrically different fillet for minimization the stress concentration. The material is assumed nonlinear while there is geometrical nonlinearity for loading. The results are compared with that of Wu who has used the fully stressed design criterion. The results show that using the ESO, the stress concentration factor is significantly redused and in this case it is reduced by 22%. In this way, the optimum shapes have completely uniform stress in the boundary of the fillet. The results show that the ESO has a superior capability for shape optimization of fillets of nonlinear structures and in this case the maximum stress is reduced by 7.7%.},
Keywords = {Evolutionary structural optimization,Nonlinear analysis,shape optimization,Stiffness Maximization},
volume = {17},
Number = {1},
pages = {157-167},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9393-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9393-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Ganjidoust, Hossei},
title = {The Application of Membrane Technologies in Waste Water Treatment of the Desalting Plants},
abstract ={The objective of this study was to evaluate the feasibility of treating desalting plant produced water to meet the applicable discharge limits and injection to well standard consistently using membrane processes to either reduce the risk of clogging of the injection well. The effluent of sand filtration unit from Aghajari maroon 2 produced water treatment was used as a feed. A Pilot scale hybrid membrane unit with a spun polypropylene 0.45 µ pore size microfilter and a hollow fiber polypropylene 0.1 to 0.01 µ pore size ultrafilter membrane was used in this study. Trials on different membrane fluxes were conducted for three processes: microfiltration, ultrafiltration and hybrid micro and ultrafiltration process. Results have shown that flow rate of 32 LPM was more applicable. The optimal flux was 120 LMH. The average percentage removal of Turbidity, Oil and grease, TSS and particle size was 98.53, 98.81, 98.23 and 99.93 respectively. The results showed that the quality of the product consistently met the requirement for injection to well. It was concluded that it is feasible to treat the produced water using micro and ultra filter.},
Keywords = {Produced water,desalting plant,membrane filtration,microfiltration,ultrafiltration},
volume = {17},
Number = {1},
pages = {167-179},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7451-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7451-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Katebi, Javad and Shoaei-parchin, Mo},
title = {Design of optimal controller for structures using differential evolution algorithm},
abstract ={One of the most important goals of optimal control of structures is the achieving the desired reduction in responses using minimal control forces. In many research efforts that have been studied over the past few decades in the field of active control, several control algorithms have been proposed that most of them calculates the required control forces by optimizing a second-order performance index. There are simplifying assumptions in formulation of these classic algorithms and constraints in mathematical optimization techniques that have been used in optimizing the performance index, for example, because of unknown nature of earthquakes, the LQR classic controller don’t consider the external forces such as earthquake excitation in calculation of control signal. This may make difficult to finding the optimal solution in optimization process and obtained relatively optimal solutions for optimization problem. Metaheuristic optimization methods, such as differential evolution are modern algorithms and because of their special capabilities in finding global optima are powerful tools that can be used in solving of complex problems. But despite the many advantages, these methods has not been used extensively for solving civil engineering problems especially in field of active control of structures. In this paper we considered the active control of structures as an optimization problem and proposed a controller that used the differential evolution metaheuristic algorithm for finding gain matrix elements of active control problem. The gain matrix elements were globally searched by differential evolution algorithm to minimizing the LQR performance index. Because of the proposed method is repetitive and does not need to solve the Ricatti differential equation; it is possible to consider the effect of external excitation in finding the gain matrix and calculation of control signal. The controller was applied on sample 2DOF and 10DOF structures and responses of these structures under the excitation of several historical earthquake records were obtained by MATLAB programming. In addition to the performance index, the maximum control force and maximum control displacement, 9 benchmark indexes that measured in controlled structures are calculated in this study. These indexes represented the reduction of controlled maximum and average responses of structure in comparison with uncontrolled responses. In order to evaluate the effectiveness of the proposed controller, these 9 performance index for 2DOF and 10DOF examples against 7 historical earthquakes for proposed and LQR controller was calculated and compared. The simulation results indicate that the proposed method is effective in keeping the controlled responses of structures in desired range and reducing the vibrations of structures with lower need to control energy in comparison with LQR algorithm. Because of great capabilities of DE algorithm in searching large spaces and the iterative nature of controller unlike the LQR method, this controller consider the effects of external forces in control process. Numerical simulation showed that the performance of the presented control algorithm is better than the LQR controller approach in finding of optimal displacements and control forces. Therefore, metaheuristic algorithms such as differential evolution can be used in active control of structures to achieving more efficient results in comparison with classic controllers.},
Keywords = {active control,Metaheuristic,Differential evolution,Optimization},
volume = {17},
Number = {1},
pages = {179-191},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-2987-en.html},
eprint = {http://journals.modares.ac.ir/article-16-2987-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Kamranirad, Reza and SoltaniMohammadi, Masou},
title = {Tension Stiffening Modeling of Steel Fiber Reinforced Concrete},
abstract ={Adding steel fibers to reinforced concrete improves the active mechanisms on crack surface including tension and shear transfer mechanisms. In Steel Fiber Reinforced Concrete (SFRC), tensile stresses are developed in fibers and deformed reinforcing bars just after crack initiation. With this beneficial effect, concrete tensile strength is improved and crack spacing decreases. In this research, SFRC member behavior is analytically investigated under pure tension and in order to verify the model, the results are compared with some recent experimental results. From the viewpoint of constitutive modeling of RC elements, there are two main approaches, discrete crack and continuum level models. The major disadvantage that adheres to discrete crack models is the fact that these models focus on the local crack behavior and seek to detect the crack paths which of course requires a high computational cost. By contrast, continuum level models taking advantage of the spatially averaged models between two primary transverse cracks. In a process of developing average constitutive models, it is important to model local mechanisms, these mechanisms in a reinforced concrete domain are related to initiation and propagation of cracks. In this article, the tension stiffening model is developed considering all effective local stress transfer mechanisms including tension behavior of deformed bar, fibers pullout, tension softening of plain concrete and bond slip-stress between the reinforcing bar and concrete matrix. Straight and end hooked fibers have different mechanisms during pullout such as debonding, friction and mechanical anchorage of end hooked fibers. To predict the fiber tensile behaviors, it is necessary to define fiber stress transfer mechanism on the crack surface. The most important parameters that affect fibers behavior are material, size and geometry, distribution and orientation of fibers. The model used in this research considers a uniform random distribution for fiber’s geometrical location and inclination angle. In this model, the slip occurred in the fiber is considered in both sides of fiber embedded in concrete. The bond slip- stress behavior of straight fiber is defined as linear before the bond stress reaches to the bond strength then the bond stress is considered constant until complete pullout. In end hooked fibers, in addition to debonding and friction, end mechanical anchorage of the fiber has also an important effect on the bearing capacity. In fact, in the process of fiber pullout, hooked part of fiber most have plastic deformation.To simulate it, a parabolic model is used. In order to solve the algorithm, an iterative analysis method is applied to calculate tension stress-elongation of specimen. To increase the accuracy of the model, the local yielding of reinforcing bars and matrix damage at the crack surface are also numerically simulated. Model verification is carried out by comparing computational predictions with available experimental results. The results show good agreement with test results. The proposed model is also shown to be useful in considering the effect of various percentage of fibers on average stress strain behavior of deformed bar, total load elongation of specimen, crack spacing and concrete tension stiffening. By increasing fiber percentage, crack spacing will decrease so the average stress strain behavior of deformed rebar become more likely to bare bar.},
Keywords = {Fiber reinforced concrete,Tension stiffening behavior,Steel fiber,average stress field},
volume = {17},
Number = {1},
pages = {191-203},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7284-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7284-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Khaji, Naser},
title = {Vibration-Based Damage Identification of Masonry Walls Using Distinct Element Modeling},
abstract ={Dry-joint masonry structures are one of the oldest building techniques from ancient and historical masonry buildings. This method used in building of historical structures that are highly vulnerable today. Also in many masonry structures, mortar strength is affected strongly by duration of time and corrosion, so the structure behavior is more likely dependent on the dry-joint characteristics. To assess the existing damages of masonry walls, non-destructive dynamic-based methods are attractive tools as they are able to capture the global structural behavior. In micro-modeling method of this paper, masonry walls are represented by Distinct Element Method (DEM) as assemblies of units consist of block and mortar, which represent an idealization of their discontinuous nature governing their nonlinear mechanical behavior. Due to the heterogeneity and the complexity of the interface’s behavior between blocks and mortar, DEM seems to be the best-adapted to model this kind of structures, in particular for reproducing complex nonlinear post-elastic behavior. At the first step, micro-modeling strategy is used for masonry walls by DEM, and particularly post-elastic behavior is verified with valid experimental data. However, DEM does not directly obtain natural frequencies and mode shapes of the wall via a classic vibrational analysis. Therefore, the second objective of this study is to propose a technique to indirectly identify dynamic characteristics of masonry walls using DEM. The aim of the part is to check the capability of dynamic identification procedures, in the extraction of the dynamic characteristics of the masonry wall in the used DEM software. For this purpose, the dynamic behavior at low vibration levels of an existing masonry building subjected to forced hammer impact test, was investigated. By transforming data collected from dynamic response of the wall, from the time domain to the frequency domain, using Fast Fourier Transform (FFT), we can find natural frequencies from Fourier amplitude spectrum. The proposed technique is then validated by comparison with the results of modal analysis which was carried out using Finite Element Method (FEM). The dynamic characteristics of walls (i.e., natural frequencies and mode shapes) may change when different levels of damage are induced in the wall. The proper knowledge of these variations is a key issue in order to study the seismic demand and seismic performance of structures. Aiming at finding adequate correspondence between dynamic behavior and internal crack growth, several numerical simulations are performed, progressive damage is induced in the wall, and sequential structural frequency identification analysis is then performed at each damage stage. In this paper, frequency and drift are selected as dynamic behavior and crack growth indices, respectively. Quantifying the relative frequency drop shows, despite the shape does not vary significantly with increasing damage, there is a relation between frequency drop and damage variations, based on analyzed data. These properties are firstly modified in the elastic range, and then is developed in the inelastic range with increasing damages. It is also observed that while the failure mode of the wall is diagonal cracking, the in-plain vibration mode shapes are much affected by initiation of crack. On the other hand, modal properties of out-of-plane mode shapes undergoes fewer effects by the diagonal crack.},
Keywords = {damage identification,masonry walls,Distinct Element Method,frequency drop},
volume = {17},
Number = {1},
pages = {203-216},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-3783-en.html},
eprint = {http://journals.modares.ac.ir/article-16-3783-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Mossaiby, Farshi},
title = {Optimal implementation of exponential basis functions method on different software platforms and performance comparison},
abstract ={Despite the success and versetality of mesh based methods and the finite element method in particular, there has been a growing demand in last decades towards the development and adoption of methods which eliminate the mesh, i.e. the so called meshless or meshfree methods. The difficulties in generation of high quality meshes, in terms of computational cost, technical problems such as serial nature of the mesh generation process and the urge of parallel processing for today’s huge problems has been the main motivation for researches conducted on this subject. Apart from these, the human expertise required can never be completely omitted from the process. The problem is much more pronounced in 3D problems. To this end, many meshless methods have been developed in recent years where, among others, SPH, EFG, MLPG, RKPM, FPM and RBF-based methods could be named. The exponential basis functions method (EBF) is one of these methods which has been successfully employed in various engineering problems, ranging from heat transfer and various plate theories to classical and non-local elasticity and fluid dynamics. The method uses a linear combination of exponential basis functions to approximate the field variables. It is shown that these functions have very good approximation capabilities and using them guarantees a high convergence rate. These exponential bases are chosen such that they satisfy the homogenous form of the differential equation. This leads to an algebraic characteristic equation in terms of exponents of basis functions. From this point of view, this method may be categorized as an extension to the well-known Trefftz family of methods. These methods rely for their approximation of the field variables on a set of the so called T-complete bases. These bases should satisfy the homogenous form of the governing equation. They have been used with various degrees of success in a wide range of problems. The main drawback of these methods however lies in determination of the bases, which should be found for every problem. This problem has been reduced to the solution of the algebraic characteristic equation in the exponential basis functions method. The method is readily applicable to linear, constant coefficient operators, and has recently been extended to more general cases of variable coefficient linear and also non-linear problems. The relative performance of usual programming languages like C++ to mathematical software packages like Mathematica and/or Matlab is one of the major questions when using such packages to develop new numerical method, as this can affect the interpretation of performance of newly developed methods compared to established ones. In this paper the implementation of the exponential basis functions method on various software platforms has been discussed. We examine C++ and Mathematica programming as a representative of different software platforms. On each platform we implement the exponential basis function method using various options available. The relative performance of these implementations is thoroughly investigated. The results show that with a proper implementation, the numerical error of the method can also be decreased considerably. In this research we show that using optimal implementations of on both platforms, this ratio is between 2.5 and 6.},
Keywords = {Exponential basis function method (EBF),Pseudo-Inverse,Singular value decomposition (SVD),Partial differential equations (PDE),Optimal implementation},
volume = {17},
Number = {1},
pages = {217-233},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7344-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7344-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Mansoori, Mobi},
title = {Perimetral joint and pulvino effects on the behavior of arch dam built on weak rock foundation},
abstract ={Design and construction of an arch dam need two essential conditions: good rock foundation and convenient topography. When these two conditions are satisfied, arch dams would be the most desirable and the most economical type of dams. Sometimes the geometry of the valley is good, but the rock foundation is not appropriate or the rock has good material but the geometry of valley is poor. One important factor in safe design of an arch dam is the rock foundation stability problem when a large part of the external loads is transferred to the foundation by the arches. In arch dams, these forces are much larger than similar forces as compared with other dams. Moreover, the stability of an arch dam also depends on bearing capacity of the rock foundation. The idea of construction of arch dams with perimetral joint and pulvino was introduced by Italian engineers in the 40s to improve stress conditions. It was gradually expanded in the following decades. Pulvino is a thick concrete pad built between the arch dam body and the rock foundation as a strip foundation. Use of this structural component, reduces the uncertainties of the rock foundation, enabling a thinner body for the dam. Thus providing perimetral joints between the pulvino and the dam body; ensures more symmetrical distribution of stresses within the dam body. It also reduces potential tensile stresses at the boundaries of the dam body. In this study, the effect of pulvino is investigated on the behavior of an arch dam body built in a valley with weak rock layers. The results are compared with the case of a conventional arch dam (Control Dam); i.e., without pulvino in the same valley conditions. In order to maintain the same concrete design properties, the volume of the Control Dam had to increase by 40% in respect to the total volume of the dam with pulvino. The foundation has a weak layer in different situations identically for both dams. The only nonlinearity accounted for, corresponds to the perimetral joints. Applied loads include the weight and the hydrostatic pressure. The dam weight is applied step by step to simulate the staged-construction of an arch dam. The ANSYS 12.1 program is used to create the finite element models of the objective arch dam and its foundation. Results of this study show that use of pulvino causes symmetric and uniform distribution of stresses in the dam body even if the rock layers are weak and asymmetric. Contrary to the Control Dam case, higher tensile stresses occur only inside the pulvino and thus the main body of the dam is protected against such stresses. As pulvino is usually reinforced, the dam with pulvino and its perimetral joint remain acceptable. Thus, despite a rather expensive and harder construction job for such dams with pulvino and perimetral joints, their considerably lower concrete volume may well compensate the problem. Thus this type of arch dam remain still economic and competitive for the future designs.},
Keywords = {Arch dam,Pulvino,Perimetral joint,Rock foundation,Weak layer},
volume = {17},
Number = {1},
pages = {233-243},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9071-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9071-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {mousavi, shakiba and ziyaeefar, mansour},
title = {Behavioral model for a Contractable Viscous Dashpot},
abstract ={Damping is one of many different methods that have been proposed for allowing a structure to achieve optimal performance when it is subjected to seismic, wind, storm, blast or other types of transient shock and vibration disturbances. Conventional approach would dictate that the structure must inherently attenuate or dissipate the effects of transient inputs through a combination of strength, flexibility, and deformability. The level of damping in a conventional elastic structure is very low, and hence the amount of energy dissipated during transient disturbances is also very low. During strong motions, such as earthquakes conventional structures usually deform well beyond their elastic limits, and eventually fail or collapse. Therefore, most of the energy dissipated is absorbed by the structure itself through localized damage as it fails. The concept of supplemental dampers added to a structure assumes that much of the energy input to the structure from a transient will be absorbed, not by the structure itself, but rather by supplemental damping elements. Fluid viscous dampers are known as energy dissipating devices with high capacity in reducing seismic effect on buildings Fluid dampers which operate on the principle of fluid flow through orifices have found numerous applications in the shock and vibration isolation of military and aerospace hardware and in wind vibration suppression of missile launching platforms. fluid Viscous damping reduces stress and deflection because the force from the damping is completely out of phase with stresses due to flexing of the columns. This is only true with fluid viscous damping, where damping force varies with stroking velocity. Other types of damping such as yielding elements, friction devices, plastic hinges, and viscoelastic elastomers do not vary their output with velocity; hence they can and usually do, increase column stress while reducing deflection. Determination of mechanical characteristics of these devices is usually based on experimental studies using cyclic tests with different amplitudes and frequencies. In this work, a new type of viscous damper is chosen for experimental studies in which the main body of the devices has been made of contractible steel bellows (developed in IIEES). The nominal force capacity of dashpot is about 500kN and its maximum stroke is around 150 millimeters. Maximum axial force in damper device will be reached about 300kN during the test. A model for representative the above viscous device should also include axial flexibility for device in the form of Kelvin or Maxwell models. Finally this model represents the general behavior of the damper based on various factors that effects its performance. In this study, a nonlinear viscous behavior has been shown in the device with respect to velocity. During Cyclic test the average of initial frictional force is about 10kN, which can be used as a functional fuse for damper. In addition, the damping force, a second friction force is about 50kN that depends on oil pressure, which increases the capacity of damper and improve its behavior. Results show that the friction force can be considered as an effective factor involved in energy dissipation of dampers.},
Keywords = {Viscous Damper,Dissipating Devices,Mechanical Characteristic},
volume = {17},
Number = {1},
pages = {234-253},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8809-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8809-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {ansari, mokhtar and ansary, maeu},
title = {Vertical Earthquake Component Effect on Seismic Demand of Medium Rise Concrete Frames},
abstract ={According to the structural damages observed after the recent near-field earthquakes which are attributed to the vertical component of the ground motion as well as concentration of the damages in column members leading to progressive structural collapse, investigation of ground motion’s vertical component effect has been widely regarded in recent studies. This component is considered less than other component of earthquake and the seismic design codes has been little attention. While the earthquake in near fault zones that has large vertical acceleration comare with horizontal acceleration, caused extensive damage. Damage of concrete columns is an example of the negative effects of the vertical component. vertical component of earthquake is considered in design of spesific members on the recommendation of seismic codes such as the EC-8 and FEMA 356. the design is intended to have with the intended use of the scaled horizontal component , Design this can be done that is unrealistic and will lead to incorrect answers due to lack of stimulation due to the specific characteristics of vertical component of earthquake and structural properties in the vertical direction, also The vertical component of earthquake is less studied in seismic risk analysis. In this study, the effects of vertical earthquake excitations on medium-rise concrete moment frames are investigated in two separate stage including near field and far field records. In this research, various structural models rep resentative of real structures designed in accordance to seismic codes and under actual gravitational loads have been subjected, simultaneously, to horizontal and vertical components of near- and far-field ground motion records at two stages. Nonlinear time history and progressive dynamic analyses have been performed in this regard. Furthermore, the effect of elevation or reduction of initial gravitational forces as well as columns’ initial axial forces have been investigated by applying differing gravitational loading coefficients. Structural response parameters including tensional and compressional axial loads of the columns as fluctuating forces, columns’ uplift forces at various plan positions and under various gravitational coefficients, the interactive axial-flexural forces of the columns at different gravitational coefficients, shear demand-to-capacity of columns, axial deformation of the columns in presence and absence of vertical component of the earthquake, have been comparatively investigated and the effect of vertical ground motion component has been assessed, separately, for far- and near-field acceleration records and for external and internal columns placed at different stories. The obtained results reveal that tensional uplift forces are more critical in external columns than the internals. This is mainly true for lower stories while at the upper stories the tensional forces experienced by internal columns are seen to be more critical. Existence of vertical component of the earthquake leads the minimum compression forces to increase and change toward tension range. The amount of this reduction has been shown to reach the value of 84% in the more extreme case. It was also seen that for smaller gravitational coefficients, tensional axial forces are more frequently observed. Presence of earthquake’s vertical component has been shown to amplify the columns’ shear demand by values that reach 31% at the most extreme cases.},
Keywords = {Vertical component of earthquake,Axial Force,Shear Demand VS Capacity,Near-field earthquake},
volume = {17},
Number = {1},
pages = {253-261},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-2263-en.html},
eprint = {http://journals.modares.ac.ir/article-16-2263-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Ahmadi, Jamal and Panahi, Alirez},
title = {Effect of Internal Curing On Mechanical Properties and
Durability of High-Strength Concretes},
abstract ={HPC has become popular due to its superior mechanical and durability properties.HPC signiﬁcantly reduces maintenance costs and enhances service life. Internal curing of high performance concrete (HPC) by pre-saturated lightweight aggregates is a wellestablished method of counteracting self-desiccation and autogenous shrinkage. However, by introducing the internal water reservoirs strength and durability properties can be injured. Concrete is a strong and durable material that has been utilized since the beginning of civilization. It is understood that many of the early structures are deteriorating or have already deteriorated away; however, with the knowledge of the material properties of concrete that is available, it is hard to imagine that concrete structures is prematurely failing before their intended service life. There are many factors involved in these failures, some of which are due to environmental conditions and others which have arisen from human errors or lack of knowledge. Early age properties of concrete are vital to its long-term performance. Many contractors and owners are interested only on the strength of concrete in 28 days or 90 days, that they overlook the importance of other early age issue especially when the mix design has water to cementitious material ratio (w/cm) lower than ~0.42. Internal curing with LWA has been successfully used recently in large construction projects of normal density concrete structures. For example, in January 2005, about 190 000 m of internally-cured concrete was used in a large paving project in Hutchins, Texas. Although the benefits of internal curing for high-performance concrete structures have been evidenced in the laboratory and some field investigations (such as those previously mentioned), the literature does not provide any significant quantitative information regarding the additional extension of the service life that can be achieved by the use of internal curing in concrete structures. A great concern for design engineers and contractors is whether the concrete will achieve the specified compressive strength and all durability requirements in the structure during service. Cusson & Hoogeveen (2008) demonstrated that internal curing can reduce autogenous shrinkage considerably without affecting the strength and stiffness of high-performance concrete. This was achieved by reducing the amount of mix water in the concrete by an amount equal to that used in the LWA for internal curing, thus reducing the effective watercement ratio (w/c ) of the concrete when using higher quantities of pre-soaked LWA. Tests by the widely accepted methods of durability assessment, such as resistance to chloride penetration, air permeability, water absorption, autogenous and drying shrinkage and mass loss, were conducted on HPC mixes made at water to cement ratios in the range of 0.21–0.33. The effect of internal curing on the durability related properties of high-performance concretes as a function of water to cement ratio is reported.},
Keywords = {High-performance concretes,Internal Curing,Light weight aggregate},
volume = {17},
Number = {3},
pages = {1-8},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4867-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4867-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Design of gravity quaywalls via nonlinear analysis of soil-quay ineraction},
abstract ={There are several quay types parallel to the shore line such as the walls constructed by piles, sheetpiles or gravity walls. Among these types of structures, the gravity quaywalls are widely used because of their simplicity of structure and ease of construction. Usually, it is the best alternative particularly in the locations with acceptable soil strengths. Weight of the blocks provide the stability of the quaywall against overturning and sliding and therefore, their dimensions are determined based on the applied loads on the quay structure. The most important load is the soil pressure that increases the lateral loads acting on the quaywall particularly during an earthquake condition. For design, the soil pressure usually converts into a static load by utilizing the seismic coefficient method. Analytical equations such as the Mononobe-Okabe formula are usually employed to calculate the applied soil pressure. However, some researchers believe that these analytical formula do not appropriately express the real behavior of the soil, and therefore, they can not be used for a proper design. There are, actually, some simplified assumptions in calculating the applied soil pressure those decrease the accuracy of the commonly used methods for quaywall design. The main assumptions are neglecting the nonlinear behavior of the soil and neglecting the flexibility of quay blocks. Due to the importance of the soil pressure in the quaywall design, these assumptions are investigated numerically in this study by making use of two well known FLAC and ANSYS softwares. For this purpose, the quaywall of Shahid Beheshti port is selected as a case study and the soil pressure around this quaywall is calculated by modeling the nonlinear behavior of the soil via using the Mohr-Coulomb constitutive model. In addition, the effect of the block rigidity on redistribution of the soil pressure beneath the quay structure is studied by a 3-D modeling of the lowest block located on linear springs (representing the supporting soil). To study the importance of each above mentioned assumption individually, two seperated models are utilized separately. According to the results, the pressure distribution under the quay wall is more uniform in the case of employing the nonlinearity of the soil. The total pressure is, however, less than the total calculated pressure by analytical formula that shows the Mononobe-Okabe formula are not accurate, but its results are overestimated for the studied problem. In addition, results show that the simplified methods can not be used for design of the lowest block because the value and the location of the maximum moment along this block changes due to its rigidity. As a result, neglecting the block deformations what is done in simplified methods is not acceptable for design purposes. It should be noted that the lowest block is so important is providing the global stability of the quaywall because its failure can lead to a total failure of the quaywall. On the other hand, all blocks are supported on this block and consequently, its repair would be too difficult even in the case of any small failure.},
Keywords = {Gravity quaywall,Soil pressure,Block rigidity,Nonlinear beahavior,Numerical analysis},
volume = {17},
Number = {3},
pages = {9-20},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5176-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5176-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Ouhadi, Vahi},
title = {Development and Validation of the Modified Barium Chloride Method for CEC Measurement and Determination of Accurate Exchangeable Calcium Cation Concentration in Carbonated Clayey Soils},
abstract ={Cation exchange capacity (CEC) is known as the main geo-environmental characteristic of the soil in which in uncontaminated soils it is a direct function of soil swelling, cohesion, and specific surface area. According to the results of the several researches the current method for determination cation exchange capacity and exchangeable cations in carbonated soils has faced to several problems due to the solubility of calcium carbonate. Carbonated soils can be found in many parts of Iran, therefore, in this type of soil, it is essential to study the impact of carbonate calcium concentration of soil upon the measures quantity of soil CEC. In addition, the selection of optimum soil weight for CEC experiment is a common problem in previous researches. The objective of this research is to develop and to validate the modified barium chloride method for CEC measurement and determination of accurate exchangeable calcium cation concentration in carbonated clayey soils. To achieve this objective, the current method of barium chloride is modified by saturation of exchangeable electrolyte with calcium carbonate. In this step, the dried sample of bentonite with the initial weight of 0.3, 0.5, and 0.7 grams were mixed with 30 ml of 0.1 M BaCl2 for two hours period. Then, samples was centrifuged at 2500 rpm for a 5 minutes period. The achieved electrolytes was used for analysis of exchangeable cations and the measurement of barium concentration. Generally, by the use of the current barium chloride method for CEC measurement of carbonated soils, one observes an increase in the measured quantity of CEC of a single soil sample as its carbonate concentration increases. This can be attributed to the solubility of calcium ions and precipitation of barium ions which cause a wrong measured quantity for CEC. Furthermore, for validation of the proposed modified method, a bentonite sample was de-carbonated with acid. The cation exchange capacity of this sample was measured before and after de-carbonation. Moreover, the CEC was measured for laboratory added calcium carbonate to the de-carbonated bentonite. The achieved results show around 60% reduction in the measured quantity of CEC of bentonite in the proposed modified method in comparison to the common barium chloride method. This is attributed to the prevention of the precipitation of barium in the modified method. In addition, according to the achieved results in the validation section of this research, the reduction of the deviation of CEC and summation of exchangeable cations, in some cases was around 80%. For instance, for a sample with initial weight of 0.3 grams, the measured quantity of calcium ion is decrease from 66.45 to 8.09 cmol/kg-soil. The achieved results show that in the modified method the measured quantity of CEC and the summation of exchangeable cations was independent to the weight of carbonate in the soil sample and soil: electrolyte ratio. It should be emphasized that according to the results of this paper, the standard deviation and coefficient of variation of the proposed modified method show 5 to 12 times reduction in comparison to that of for the current barium chloride method.},
Keywords = {Cation Exchange Capacity,Bentonite,Carbonate Calcium,Barium Chloride,Calcium Ion},
volume = {17},
Number = {3},
pages = {21-34},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7427-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7427-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Izadi, Amin and Aghakouchak, Ali Akbar},
title = {Numerical study of cyclic and failure behavior of built-up concentric braces containing double angle sections},
abstract ={The most important characteristic of brace frames is their significant and appropriate stiffness as well as their compression strength against earthquake forces. Built-up special concentrically braced frames (SCBFs), which contain double angle braces, are among the common steel structural systems resisting lateral loads. Along the built-up brace length, the stitch and connector distances make significant role in cyclic and ductility behavior of braced frames due to possibility of out of plane buckling.The results of experimental studies of built-up double angle braces illustrate that setting the stitches closer to each other can improve the post buckling behavior of systems, resulting in increasing the final compression strength, close to box-shaped brace strength. In addition, an individual member buckling is possible by increasing the stitch distances along built-up braces. According to AISC seismic provisions regarding built-up SCBFs, the slenderness ratio of individual elements between the connectors should not exceed 0.4 times the governing slenderness ratio of the built-up member. Also, connecting built-up members by the use of welding is not permitted within the middle one-fourth of the clear brace length. In fact, AISC seismic provision has prohibited the use of stitches and connectors in the protected zones of built-up specially concentrically braced frames such as the center one-fourth of the clear brace length and a zone adjacent to each connection equal to the brace depth in the plane of buckling. In this research, seismic provisions related to built-up diagonal and X-braced SCBFs are numerically investigated under cyclic loading using a single-bay single-story frame. The numerical study is performed on models, which contains parameters such as back-to-back and face-to-face connection types of built-up members. Seismic behavior of these braces are investigated from the view points of cyclic and failure behavior. This investigation is performed on both types of diagonal and X-braced steel frames. The cyclic behavior of systems is studied based on post buckling capacity, structure initial stiffness, and final compression strength. Failure behavior of systems is investigated with regard to failure cycle and ductility capacity. In order to evaluate of seismic behavior and ultimate ductility of the numerical models, regarding to proximity of initiation and propagation of steel cracks, the concept of plastic equivalent strain is used to predict system failure. The results of this study show that increasing the number of stitches or decreasing their distances along the length of the built-up members may not necessarily improve behavior of braced systems.That means inelastic deformation consent will probably occur in individual elements between stitches resulting in earlier failure of braces. Therefore, current seismic provisions such as not exceeding the slenderness ratio of individual elements between stitches from 0.4 times of the governing slenderness ratio of the built-up member for compression sections, are conservative in SCBFs and can be changed according to the type of braces. In addition, Failure of double angle back-to-back diagonal braces occurs sooner in comparison to face-to-face braces. Also, in X-braced frames, cyclic and failure behavior of built-up face-to-face braces are more desirable than the similar back-to-back braces in general.},
Keywords = {Build-up concentrically braced frames,double angle,plastic equivalent strain,back-to-back,face-to-face},
volume = {17},
Number = {3},
pages = {35-46},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5035-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5035-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Bathaei, Akbar},
title = {Investigation of the effects of vertical link beam length on steel structures residual displacement},
abstract ={There is a debate among earthquake engineers that the structural and non-structural damages initially occur due to lateral loads caused by earthquake excitation. American provisions, including FEMA356 estimates structural performance by means of maximum deformation demand. However, in addition to the maximum deformation, residual displacement plays an important role in structural performance. Amplitude of residual displacement is an important parameter in technically and economically determining rehabilitation of damaged structures for resisting aftershocks. In this study, residual displacements of a five-story steel frame is designed with vertical link beam as well as the effect of vertical link beam length have been investigated. For vertical link beam, the IPE sections with typical steel is considered, instead of using boxes and H-shaped cross-section.The IPE section has some advantages than box section such as lower cost, easier installation and replacement. The Vertical link beams with IPE cross-section has been studied in 5 separate models with length of 20, 25, 30, 35 and 40 centimeters. In this paper, experimental results of a frame model with vertical link beam tested in structural laboratory of Building and Housing Research Center (BHRC) has been used for verification of numerical model. As one of the fastest nonlinear softwares, OpenSees (Open System for earthquake engineering simulation) has been used for structural modeling. The steel material that has been used in this model is uniaxial material steel 02. In the following, seven near field and seven far field earthquake acceleration time histories that scaled by 2800 standard, are used analysis of five-story and five-bay structure with chevron bracing system. According to the seismic design of structures if ductile elements is used in a structure, then beams and columns should remain elastic during earthquake, while ductile elements dissipate input energy by nonlinear behavior of ductile members. By considering of the results, the vertical link beam with length of 20 and 25 centimeter for far field earthquakes and 20 centimeter for near field earthquakes have the best performance compare to the other cases. The Bam earthquake is selected to investigate of hysteresis diagram of the vertical link beam energy dissipation. The results for near field earthquake like the Bam earthquake show that link beam with length of 40 centimeter with moment behavior, has low energy dissipation capability. Furthermore, the vertical link beam with 40 centimeter length causes more residual displacement and yielding. By considering the station with equal 104.28 km distance from center of earthquake can use the Bam record as a far field earthquake. In this case link beams with more than 25 centimeter length have more fluxing. However, the link beams with length of 20 and 25 centimeter have better seismic performance. Considering the RMS (Root Mean Square) parameter as a controller criterion the vertical link beam with length of 20 centimeter is more suitable for near and far field earthquakes. Considering the seismic performance parameters of vertical link beam like appropriate stiffness, high stability, energy dissipation capability, appropriate control of maximum response of structure and less residual displacement, the vertical link beam with length of 20 centimeter has the best seismic performance for near and far field earthquakes compare to the other cases.},
Keywords = {Vertical Link Beam,Residual Displacement,Near Field Earthquake,Far Field Earthquake},
volume = {17},
Number = {3},
pages = {47-60},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7834-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7834-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Khaiatrostami, Babak and Hassanzadeh, Yousef and Khaiatrostami, Siamak},
title = {Study of Backwater and Hydraulic Jump Phenomena in Historical Bridges by Computational Fluid Dynamics},
abstract ={Establishing a bridge in a waterway changes flow characteristics. Most of these changes derive from geometric details of bridge. Circular and pointed (nested) arches have been used as opening geometry in historical bridges. Historical bridges are valuable heritage and protection of them is important because of cultural continuity. Hydraulic study is a tool to recognize these structures and their design philosophy. In this research, effect of three opening geometry on backwater and hydraulic jump phenomena was numerically studied by Flow-3D software. The FLOW-3D software was selected because not only previous studies indicated that flow around a bridge as well as in a compound channel involves significant 3D characteristics but also it is a powerful hydraulic engineering design tool to model 3D free surface flows. The performance of FLOW-3D was tested using of experimental data obtained from test series which were conducted at the Hydraulic Laboratory, Birmingham University on two opening semi circular bridge model in compound channel (AMOSEC) in which the width of model was 0.10 m. Laboratory tests were carried out for low flow conditions without flow contact with the lower bridge deck (21 to 35 lit/sec). In order to study submerged (High Flow) condition, a program has been developed in the MATLAB environment to extrapolate discharges and related normal depth for 40 to 60 lit/sec discharges. Three opening geometry with the same area as AMOSEC model designed in the AutoCAD. DWG files converted into the Stereolithography format and imported into the Flow-3D.The computational domain, 18 m long and 1.213 m wide, was divided into structured grids. This domain involved nonuniform rectangular grids of 950, 100 and 26 to 40 cells in the x-, y- and z-directions, respectively. Inflow boundary condition was specified as discharge. The downstream boundary condition was specified with a constant fluid height equal to the uniform depth. The sidewalls as well as the channel bottom were defined to be no slip boundaries. On the top, the symmetry (atmospheric) boundary condition was assigned to describe the free surface flow condition. Measured uniform flow depth with zero velocities for each run was assigned to each computational cell to set the initial flow condition. Free surface modeled by VOF and turbulence by two equation K-ɛ methods. Then, a total of 27 runs carried out until steady state resulted. The results indicate that pointed arch geometry makes maximum afflux for both low flows (sub-soffit) and high flows (super-soffit) conditions in all models. Emerging Location of afflux at longitudinal axis is the same for all of the models. Length of hydraulic jump for pointed arch geometry is maximum under low flow condition and minimum under high flow condition. Hydraulic jump starts near the pier for rectangular opening geometry in comparison with others. Critical shear stress due to hydraulic jump is minimum for rectangular geometry and maximum for pointed arch in all discharge conditions. Circular opening geometry produces less upstream flooding and less possibility of downstream bed destruction, so it has advantages on pointed arch geometry.Out of the structural reasons, whole of these results may be considered as hydraulic reason of evolution of pointed arch to semi circular geometry from Safavid to Qajar era.},
Keywords = {Flow-3D,Backwater,Hydraulic jump,Flow-3D,Historical bridges,Opening geometry},
volume = {17},
Number = {3},
pages = {61-69},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6639-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6639-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {GhanooniBagha, Mohammad and Asgarani, saee},
title = {Influence of effective chloride corrosion parameters variations on corrosion initiation},
abstract ={Reinforcement inside the concrete is protected from corrosion and its damages until several years after the construction. After corrosion initiation, the Cross Section of Reinforcement begins to reduce and often load bearing of the reinforced concrete structure will be reduced significantly. Corrosion of reinforcements in concrete in polluted and contaminated areas can be occurred in two ways: Chloride and Carbonation. Chloride ion ingress is one of the major problems that affect the durability of reinforced concrete structures such as bridge decks, concrete pavements, and other structures exposed to harsh saline environments. Corrosion occurrence and development in reinforced concrete structures increase the steel volume and produce products with volume of about 2-7 times the steel initial volume. This volume increase, which is due to cracks, reduces the compressive and tensile strengths in reinforced concrete structures. Therefore, durability based design of concrete structures in marine areas has gained great significance in recent decades and various mathematical models for estimating the service life of reinforced concrete have been proposed. In spite of comprehensive researches on the corrosion of reinforced concrete, there are still various controversial concepts. Effect of environmental conditions on durability of concrete structures is one of the most important issues. Hence, regional investigations are necessary for durability-based design and evaluation of the models proposed for service-life prediction. The Persian Gulf is one of themost aggressive regions of the world because of elevated temperature and humidity as well as high content of chloride ions in seawater. Corrosion of reinforcement due to chloride ions attack causes enormous damages to structures in severe condition of marine environments. Normally, high alkaline property of concrete (PH≈13) forms a protective oxide layer on the steel surface. This is called a passive protection. The dioxide existing in the atmosphere or the chloride in the concrete environment along with the moisture and the oxygen can penetrate via the concrete pores and cracks and can reach the armature surface; then, by reducing concrete alkalinity, they cause armature corrosion inside the concrete by destroying the protective oxide layer on the steel. Chloride ions reach the passive layer according to the explained pattern and they begin to react in the passive layer when the amount of chloride ions go beyond the critical value and cause perforation corrosion. Since each influencing factor in the life time of the structure is subject to random variability and inherent uncertainties, a stochastic approach is utilized to predict the time for initiation of the corrosion. Based on Fick’s law, time for corrosion is a function of surface chloride, critical chloride, concrete cover thickness, and diffusion coefficient. The most common models service-life prediction of reinforced concrete structures under load chloride, only produce a limited definite time for the start of corrosion. In this paper monte carlo simulation use for service-life prediction of reinforced concrete structures of predict the time of corrosion initiation, and shown the influence of mean and standard deviation variations for each of the parameters that affect the occurrence of corrosion, on the time of initiation corrosion and impact of these factors on the probability initiation corrosion.},
Keywords = {Reinforced Concrete Structures,Corrosion of Chloride,Durable Design,Monte Carlo simulation},
volume = {17},
Number = {3},
pages = {69-77},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9154-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9154-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {safarzadeh, A.},
title = {Three Dimensional Hydrodynamics of Sudden Dam Break in Curved Channels},
abstract ={In this paper, the dam break phenomena has been simulated in curved rivers using 3D numerical model, Flow-3D. It utilizes the finite volume scheme for structured meshes was used for solving the unsteady Reynolds-averaged Navier-Stokes equations in conjunction with the RNG k-ε closure model. In the utilized software, the Fractional Area/Volume Obstacle Representation (FAVOR) method is used to inspect the geometry in the finite volume mesh. FAVOR appoints the obstacles in a calculation cell with a factional value between 0 to 1 as obstacle fills in the cell. Fluid surface shape is illustrated by volume-of-fluid (VOF) function F(x,y,z,t). With the VOF method, grid cells are classified as empty, full, or partially filled with fluid. Cells are allocated in the fluid fraction varying from zero to one, depending on fluid quantity. The pressure and velocity are coupled implicitly by using the time-advanced pressures and time-advanced velocities in the momentum and continuity equations, respectively. FLOW3D solves these semi-implicit equations iteratively using relaxation techniques. In this paper the GMRES technique has been used as pressure implicit solver. A flux surface is a diagnostic feature in FLOW-3D for computing fluid flow rates. It can be used to obtain time-dependent information about the flow in different parts of the domain. A typical flux surface is a 100% porous baffle with no flow losses, so it does not affect the flow in any way. This feature gives the opportunity to determine the flood hydrograph at various stations downstream of the dam. Effects of curve angle and radious of curvature on the flood wave propagation and unsteady flow features along the curved reach, downstream of the dam has been investigated. Results showed that at the initial instants of the dam break in the straight channel, due to the effects of the dynamic wave, flood hydrographs at the dam location and at a distance downstream of the dam have local peak values, while in the curved chnnel cases, the flood wave becomes unstable immediately after the dam break and the local peak occures just at the dam section. The curved reach decelerate the flood wave propagation compared to the straight channel. Effect of channel curvature on the movement of the flood wave along the inner bank is higher than the outer bank and also the centerline of the curved channel. By decreasing the central radious of the bend, slope of the rising limb of the hydrograph and also the peak discharge, attenuates. Furthermore, the peak discharge time reduces. Unlike to effects of the curvature of the bend, increasing the bend angle does not affect the peak discharge. Changing the bend curvature and curve angle has no effect on the falling limb of the flood hydrograph at various stations downstream of the dam.},
Keywords = {Dam Break,River bend,Flood wave,Numerical model,Dynamic wave},
volume = {17},
Number = {3},
pages = {77-88},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7731-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7731-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {ghanizade, mohammad and SarvghadMoghadam, Abdolreza and Farzam, Masoo},
title = {Evaluation of the effective parameters on the behavior of shallow RC shear walls considering soil-structure interaction},
abstract ={Short reinforced concrete shear walls with aspect ratio less than 2 are commonly utilizes in strengthening of low rise structures. These walls demonstrate adequate lateral load strength while they have low ductility comparing with high rise walls with same lengths. Considering typical span length of such a walls– between adjacent column distances -there are no need to motivate all of lateral bearing strength of them and only taking to account a portion of strength will be sufficient for the purpose of strengthening of the structure. In this paper it will be shown that tacking into account the shape and length of foundation and interaction of the soil-structure the ductility of the wall is increased. Furthermore, effect of the soil stiffness on the behavior of the wall is studied. The short shear wall which has been studied experimentally by the NUPEC of Japan is adopted for numerical simulation by the commercial nonlinear analysis software ATENA 3D. The wall has been subjected to the predefined level of axial load and the increasing cycling lateral deformations. Sensitivity of the behavior of wall to mesh dimensions and the affecting parameters of concrete models such as fracture energy, tension softening and tension stiffening coefficient, shear modulus reduction after cracking, fixed or rotating crack modeling among the other affecting parameters are investigated to verify the model. Because of symmetry only one half of the wall is modeled. Reinforcing bars are modeled discretely taking into account the bond-slip between concrete and bars. The results of verified model are used to study the sensitivity of a proposed short shear wall by IIESE for strengthening of low rise masonry buildings, to the parameters of length and shape of the footing together with and foundation soil property. It is shown that with increasing the length of footing, base reaction coefficient and the embedment depth of footing the bearing capacity of shear walls showing rocking behavior is increased but the ductility is decreased. For structures which need a limited level of strength increase or a demanded ductility, the length or embedment length of the footing may choose intentionally to motivate the rocking behavior of foundation. Short reinforced concrete shear walls with aspect ratio less than 2 are commonly utilizes in strengthening of low rise structures. These walls demonstrate adequate lateral load strength while they have low ductility comparing with high rise walls with same lengths. Considering typical span length of such a walls– between adjacent column distances -there are no need to motivate all of lateral bearing strength of them and only taking to account a portion of strength will be sufficient for the purpose of strengthening of the structure. In this paper it will be shown that tacking into account the shape and length of foundation and interaction of the soil-structure the ductility of the wall is increased. Furthermore, effect of the soil stiffness on the behavior of the wall is studied. The short shear wall which has been studied experimentally by the NUPEC of Japan is adopted for numerical simulation by the commercial nonlinear analysis software ATENA 3D. The wall has been subjected to the predefined level of axial load and the increasing cycling lateral deformations. Sensitivity of the behavior of wall to mesh dimensions and the affecting parameters of concrete models such as fracture energy, tension softening and tension stiffening coefficient, shear modulus reduction after cracking, fixed or rotating crack modeling among the other affecting parameters are investigated to verify the model. Because of symmetry only one half of the wall is modeled. Reinforcing bars are modeled discretely taking into account the bond-slip between concrete and bars. The results of verified model are used to study the sensitivity of a proposed short shear wall by IIESE for strengthening of low rise masonry buildings, to the parameters of length and shape of the footing together with and foundation soil property.},
Keywords = {Short Shear Wall,Nonlinear analysis,Shear Strength,Strengthening},
volume = {17},
Number = {3},
pages = {90-102},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4131-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4131-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Makarchian, Masoud and gholipour, sajj},
title = {Improving the Performance of the Square Shallow Foundations using Inferior Skirts},
abstract ={Development of the new type of improvement methods of shallow foundations in the geotechnical engineering, it seems necessary to study the performance of vertical plates beneath the periphery of shallow foundations known as skirted foundations. Skirted foundations are steel or concrete foundations, which have a top raft and a relatively thin plate constructed beneath the periphery. The skirts penetrate the soil beneath foundation which encompass and confine the soil very firmly. The skirts and confined soil behave as a unit to transmit loads to the soil at the level of skirt tip. The benefit of skirted foundations compared with deep foundations such as piers and piles lies in their ease and short time of installations. The skirted foundations can be used as an appropriate alternative for shallow foundations, pier and deep foundations in applications such as oil and gas storage tanks, wind turbines, oil drilling platforms, harbor, and offshore and jacket structures. The behavior of square shallow foundations resting on confined sand by vertical plates as skirt, was studied using small scale physical modeling in the laboratory. The effects of parameters including ratio of skirt length to foundation width, foundation size, the shear strength of sand, and roughness of skirt and foundation surfaces on skirted foundations behavior in terms of increasing bearing capacity, the settlement reduction, and improvement of subgrade reaction modulus were assessed under compression loading, and results compared with the performance of shallow and pier foundations. Modeling test analyses revealed the overall improvement of square skirted foundations performance compared to shallow and pier foundations. Results of this study showed that the values of bearing capacity and settlement of skirted foundations are almost close to those of pier foundations of the same width and depth. Also, it was observed that the existence of skirt, increases the bearing capacity and modulus of subgrade reaction, together with decrease of settlement of shallow foundation. The enhancement in the bearing capacity, as well as reduction in the settlement of shallow foundations increases with increasing skirt depth and decreasing the shear strength of sand. So that, bearing capacity ratio (BCR) of skirted foundations to surface foundations was observed in the range of about 2.4 to 5.1 times for the different values of L/B. Furthermore, the value of skirted foundation settlement decreased up to 91% of that a surface foundation in the case of having skirt depth/ foundation width of 2.0. The modulus of subgrade reaction improved in the range of about 1.5 to 4.23 times duo to skirt existence. From the accomplished laboratory tests, it was found that skirted foundations resting on loose sand, are more beneficial than in case of resting on medium and dense sand. In cases where structures are very sensitive to settlement values, the skirted foundations can be used to gain the same allowable bearing capacity a much lower settlement. In this paper, based on the analysis of the obtained results, charts and equations are presented to estimate bearing capacity and settlement and subgrade reaction modulus of skirted shallow foundations in terms of those of surface foundation and sand relative density, skirt depth to foundation width ratio and its roughness.},
Keywords = {Skirted foundation,inferior skirt,bearing capacity,Settlement,Physical Modeling},
volume = {17},
Number = {3},
pages = {104-116},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4273-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4273-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {KazemiNiaKorrani, Hamid Reza and 1, 1},
title = {The Effect of Opening and Stud Spacing on Composite Shear Wall Behavior},
abstract ={Shear walls are resistant to lateral forces such as wind and earthquake. In recent decades, because of proper ductility and high strength of steel shear walls, engineers and researchers are interested to these walls. If the shear yielding occurs before buckling of web plate of wall, the wall will absorb more energy. Reinforcing steel plate shear wall would cause shear yielding occurs before buckling. In order to strengthen of wall can be used steel stiffeners or one layer of concrete. Steel shear walls with a layer of concrete to increase the strength out of plane called composite shear wall. Composite shear walls consist of a thin steel plate, two columns and two horizontal floor beams with one or two concrete layers. Considering the few studies that have been done on this type of walls, in this study, the effect of opening and stud spacing will be discussed in the behavior of the composite shear wall. Firstly, the 10-storey building with composite shear walls designed. Then upper floor selected and finite element models of this floor modeled with Abaqus. The models are one span and one story that length of span (inside into columns) and a height of story (the inside of the beams) is 3 m. Beams and columns are IPB280 and thickness of web plate and concrete layer are 2 and 100 mm respectively. It should be mentioned, to prevent local buckling column flange at the beam-column connection, in line of beam flange, continuity plate is considered. In this study to ensure the accuracy of the finite element model and ability of Abaqus to accurately estimate the actual behavior of shear walls, several shear walls model and analyze, then their results were compared with the results of the tests in the previous studies (Lubell’s test and Valizadeh’s experimental model). The results show that there is little difference between the experimental results and finite element results. So by taking a little difference can be concluded that the finite element results are acceptable. In order to compare the results of finite element models of composite and steel shear wall and steel moment frame, boundary elements and also load all three models are considered equal. Compare the results show that, on a constant displacement, the base shear in the steel shear wall is about 120% more than moment frame. Also, the base shear in the composite shear wall is 23% more than steel shear wall. Considering the results, it is evident that by reducing the distance between the studs, wall strength increases. Also, increasing web plate thickness cause to increases the capacity of the composite shear walls. Opening has always been the creation of composite shear wall resistance decreases. Opening at the sides and corners further reduces the resistance. This is unlike steel shear walls. At the end of this paper was to effect of the stud positions on the composite shear wall behavior. The results indicated that the studs closer to the external environment, resistance of composite shear wall increases. In order to compare the results of finite element models of composite and steel shear wall and steel moment frame, boundary elements and also load all three models are considered equal. Compare the results show that, on a constant displacement, the base shear in the steel shear wall is about 120% more than moment frame. Also, the base shear in the composite shear wall is 23% more than steel shear wall. Considering the results, it is evident that by reducing the distance between the studs, wall strength increases. Also, increasing web plate thickness cause to increases the capacity of the composite shear walls. Opening has always been the creation of composite shear wall resistance decreases. Opening at the sides and corners further reduces the resistance. This is unlike steel shear walls. At the end of this paper was to effect of the stud positions on the composite shear wall behavior. The results indicated that the studs closer to the external environment, composite shear wall resistance increases.},
Keywords = {Composite shear wall,opening,Stud,ductility,finite element method},
volume = {17},
Number = {3},
pages = {118-130},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8258-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8258-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Goodarzi, Amir rez},
title = {Effect of curing temperature and SiO2-nanoparticles on the engineering properties of lime treated expansive soil},
abstract ={Expansive clayey soils can undergo periodic volumetric changes in the form of ground heave and settlement when subjected to moisture fluctuations. Such changes may lead to exert stress and serious problems to geotechnical structures if not adequately taken care of. Lime continues to be commonly used for treatment of these type soils; however, some restrictions are associated with its application. Therefore, in the present study a series of macro and micro level tests including swelling potential, unconfined compression strength (UCS), consolidation, pH and electrical conductivity (EC), adsorption, X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses were carried out at various curing periods (1, 7, 28 and 90 days) and different temperatures (10, 20, and 40 °C) to assess the effects of environmental condition and SiO2-nanoparticles (NS) on the performance of lime treatment. To achieve the stated objective, lime and lime/NS (LNS) mixture were separately added to highly expandable clay at wide ranges from 0% to 30% by mass, respectively. The results obtained show that the environmental temperature, especially in the initial time of curing, has a prominent role on the geo-mechanical properties of lime treated soil samples. It was also found that the reduction in the temperature particularly at inadequate curing (lower than 28 days) provides a deleterious impact on the pozzolanic activity and decrease the formation of cementing compounds such as Calcium-Silicate-Hydrate (CSH) and Calcium-Aluminate-Hydrate (CAH) gels. In this case, the process of soil modification is mainly due to the short-term reactions (i.e. cation exchange and increase in osmotic pressure), increasing the amount of additives (up to two times) to control the swelling power. On the other hand, the incorporation of SiO2-nanoparticles into the binder system causes a reduction in the detrimental effects of low temperature on the engineering parameters of lime-treated products and decreases their sensitivity to the time of curing. The samples amended with the LNS blend exhibit a continuous development of soil mechanical capacity as the additive content increased. They are less deformable and show a decrease in their compression index by nearly 40% as compared with sole lime. Based on the XRD and SEM experiments, the superior influences of LNS are mainly ascribed to the higher and faster formation of cementitious compounds. In fact, at the presence of LNS, due to direct interaction of lime and silica from NS, the silicate gel can be immediately formed to coat and bind the clay particles together; whereas, with the addition of lime alone, the gel produces only by the removal of silica from the clay minerals that needs further time to complete its formation and hence the lower modification was occurred, especially at curing time shorter than 28 days. Moreover, NS reduces the pores sizes and serves to distribute the new crystalline phase (e.g. CSH gel) in a more homogenous fashion in the available space. This micro-structural reorganization upon the LNS treatment could rapidly block off the soil voids and greatly interlock the clay particles together that provide higher environmentally-stable materials with lower cost and energy as compared to standalone lime. It is finally concluded that the utilization of LNS mixture gives a promising way for increasing the efficiency of lime stabilization and decreasing the additive consumption.},
Keywords = {Expansive clays,Lime-SiO2-nanoparticles,temperature,Pozzolanic activity,Engineering properties},
volume = {17},
Number = {3},
pages = {132-144},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12389-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12389-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Sarafrazi, S. Rez},
title = {Dynamic relaxation with concentrated damping},
abstract ={Solving a system of linear or non-linear equations is required to analyze any kind of structures. There are many ways to solve a system of equations. They can be classified as implicit and explicit techniques. The explicit methods eliminate round-off errors and use less memory. The dynamic relaxation method (DRM) is one of the powerful and simple explicit processes. The important point is that the DRM does not require to storage the global stiffness matrix. It just uses the residual loads vector. Utilizing the virtual masses, damping and time steps, the DRM convert a system of static equations to dynamic ones. The process is started by assuming an initial solution. The next steps are done in such a way that the residual forces are decreased. The proper value of fictitious mass and time step guarantees the convergence of the proposed DR procedure. On the other hand, the convergence rate is dependent on value of damping factor, which is calculated using the lowest eigenvalue of artificial dynamic system in the common dynamic relaxation method. It is evidence; the dynamic system oscillates when damping is zero. The convergence of DRM with zero damping factors is achieved utilizing kinetic damping or -damping. In the kinetic dynamic relaxation process, the velocities of the joints are set to zero when a fall in the level of total kinetic energy of the structure occurs. However, it is difficult to calculate the extreme point of kinetic energy. Topping suggested assuming the peak point at the mid-point of the previous time-step, when a fall down in kinetic energy is occurred. The factor in the -damping method is time step ratio of two sequence steps. The time-step ratio can be calculated in such a way that the responses converge to exact solutions. In this paper, a comprehensive review of dynamic relaxation algorithms is presented. Of these, the popular and kinetic damping DR methods are described in detail. Then, the new dynamic relaxation algorithm is proposed. In this procedure, the artificial mass and time steps are similar to the DR methods that have been recently introduced. However, the damping factor is different with these methods. Damping factor is calculated in some specified steps. In other words, damping is zero in the most step of DR algorithm. Therefore, the total number of calculations is reduced. The concentrated damping is imposed, when the value of total kinetic energy of system is at its peak point. Utilizing the proper values of concentrated damping factors, the kinetic energy converges to zero. The presented formulation shows the relation between common and kinetic dynamic relaxation processes, too. It should be noted; the procedures of minimizing the kinetic energy of proposed method and Topping algorithm are different. The kinetic technique is required more calculations. Finally, some benchmark problems of truss and frame structures are selected. The linear and geometric nonlinear analyses are performed. The numerical results also show that the convergence rate of the new DRM increases in the majority of cases with respect to kinetic damping and also popular damping.},
Keywords = {Traditional dynamic relaxation,Kinetic damping,Kinetic energy,concentrated damping},
volume = {17},
Number = {3},
pages = {146-156},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8360-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8360-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Mahpour, Alirez},
title = {Modeling integrated clothing shopping destination choice using structure equation models},
abstract ={The destination choice problem is an essential element in transportation planning processes. The problem is to find the probability that a person traveling from a given origin will choose a destination among many available alternatives. The focus of this paper is the destination choice of non-work (shopping purpose) trips, as part of the transportation planning process, in particular in trip- based and activity- based models. In general, destination choice models are estimated and applied at the traffic zone level, although the actual destination is an elemental alternative inside a traffic zone. Therefore, the number of explicitly modeled choice alternatives is usually the number of traffic zones. Most destination choice models assume a Multinomial Logit (MNL) form for the problem. The Multinomial Logit is not capable of accounting for unobserved similarities among alternatives, since the covariance matrix of the MNL model has only elements in the diagonal. The purpose of this paper is to investigate alternative destination choice model structures, focusing on structure equation models. The non-work destination choice problem is studied in spatial choice modeling. The literature concerned with spatial choice models covers several disciplines and important insights can be found in spatial behavior and spatial interaction models. Trip distribution models are expressed indirectly in terms of behavior models and this issue in trip generation and trip distribution is bolder. Considering new approach to transport planning (activity- based) and modeling behavior of passengers, the activity location choice is more attended and usually discrete choice models are used. Many studies describe zonal utility (simple decision structure) by using land- use and socioeconomic variables and thus cannot describe individual behavior in disaggregate level. For describe more accurate of individual utility, recent studies, have used simultaneous choice process concept and in other hand few studies used structural equation models and latent variables in describe choice of activity location. Investigating of individual features in activity location choice by using of structure equation models considered in recent studies. Considering the importance of determining activity location in activity- based approach, use of exogenous and explainer variables are bolded. Variable in classic destination choice models firstly are supposed independently and secondly have less attention to psychological and personal feature of passengers. Considering these two points, the power and efficiency of representation of behavior are reduced. Studies on the consumer behavior in shopping centers, showed that in addition to observable demographic and socio-economic variables, latent individual variables like to psychological variable, Attitude lifestyle and shopping orientation are important and must be attendant (complex decision structure).the idea of applying these variables in modeling the individual clothes shopping destination choice by using structure equation models was sourced from ethology studies on customers of shopping centers (novelty of paper). In this paper 213 sample are collected by internet- based questionnaire and individuals socio- economic, attitude, lifestyle and shopping orientation were asked. This integrated model is able to correctly predict the 42 percent of observation in which destination number 1 (Bazar of Tehran and Plasko shopping center) has the highest percent correct.},
Keywords = {Destination Choice,Structure Equation Model,Integrated Model,Shopping Trip},
volume = {17},
Number = {3},
pages = {158-170},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1044-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1044-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Analytical Investigation of Proposed Semi-Rigid Beam to Column Frame Connections},
abstract ={Precast concrete structures have been widely used since the last century. Fast production, quick erection, higher quality, economical aspects, lower labor costs etc. are of noticeable advantages of such structures compared to that of in-situ concrete structures. Considering frame structures, connections play a vital rule in local and global behavior of precast concrete structures. Catastrophic failures and losses are incurred globally due to failure in connection regions, so connections are considered to be the weak spots in precast concrete structures. Consequently, a great amount of attention and care is required in designing and forming connections, especially in precast concrete structures. In addition, compared to monolithic structures, it is relatively more difficult and more time consuming to achieve rigidity in connections due to the nature of precasting. Plus, difficulties arising from construction and structural details will neutralize inherent characteristics of precasting. Thus, obtaining a connection with details that are simple enough to be constructed easily on site, which, of course, satisfies demanding mechanical characteristic, can be of great importance. In this paper, two new types of beam to column connections are proposed. These connections are designed, modeled and analyzed numerically using nonlinear finite element software, ABAQUS. Main goal of the research was to achieve constructible and easily erectable connection detail which can provide satisfactory lateral strength, stiffness, ductility and energy absorption. Embedded steel corbels are used as members which transmit tension due to imposed positive moment and shear in negative moment in addition to their role as seating in initial stages of construction. Continuity is provided with bolting or welding of bottom bars to the corbel and then connection area is filled completely with expansive grout. Eccentricity of transmitted forces is a decisive factor especially in dynamic loadings, thus, in design, it is minimized by adjusting bar and corbel size and position and welding locations, size and shapes. Top bars are passed through holes, previously cast into the precast concrete column and are embedded in in-situ concrete of slabs. T shaped assemblies of the connections are modeled and laterally loaded until ultimate concrete strain is reached. In terms of strength, both connections were capable of achieving 95 percent of equivalent monolithic assembly. Considering lateral stiffness, proposed connections were able to provide initial stiffness of more than 80 percent of equivalent monolithic connection. Precast connections were 20 to 30 percent less ductile than their monolithic counterpart. Noticing relative geometric complexity and difference in force transmission mechanisms of connections, lower ductile behavior of connections is justifiable. Effects of axial column load are studied on response of the assemblies. Compressive axial load relatively improves lateral stiffness and energy absorption of the connections. By imposing axial tension on column, lateral stiffness and strength is significantly reduced. Comparing before mentioned mechanical characteristics of proposed connections with their equivalent monolithic assembly, satisfactory response under lateral monotonic loading is observed. Based upon results derived from this study, proposed connections may be used as semi rigid beam to column connections in precast concrete frames, instead of fully rigid connections.},
Keywords = {Stiffness,ductility,energy absorption,monotonic loading},
volume = {17},
Number = {3},
pages = {172-182},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11646-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11646-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {motalebizadeh, mohammadreza and Shafieefar, Mehdi and ghodsian, masou},
title = {Sedimentation Position Prediction in the Swash Zone of Sandy Beaches using Response Surface Method},
abstract ={Reflective beaches requires a combination of lower waves, longer periods and particularly coarser sands. They are typically steep in beach profile with a narrow shoaling and surf zone, composed of coarse sediment. Coarser sediment allows percolation during the swash part of the wave cycle, thus reducing the strength of backwash and allowing material be deposited in the swash zoneThe Swash zone, as extreme area of inner surf zone, influences coastal area and coastal structures. It defined as the part of the beach between the minimum wave run-down and maximum wave run-up. It constitutes a beach area where waves dissipate or reflect their remaining energy after traveling towards the shore. The role of Swash zone is influenced by incoming waves from surf zone, the geometry of beach face and the interaction between beach groundwater and surf zone.The review of Laboratory researches indicated that wave height and period, beach slope, grain size distribution of beach material, still water level (SWL), beach groundwater level, the hydraulic conductivity of beach influence on the evolution of sand beaches. In a few laboratory researches, experiments is designed with One Factor At a Time method (OFAT) and the qualitative effect of parameters of regular wave height and period, SWL and beach groundwater level, and beach slope are investigated on nearshore evolution. In this research, experiments are designed using Central Composite Design (CCD) of Response Surface Method (RSM). CCD is a type of response surface design that present very good predictions in the middle of the design space. Important properties and features of CCD are orthogonality, rotatability and uniformity. The quantitative effects and interactions of irregular wave height and period, beach groundwater level and SWL, and beach slope on beach profile evolution is examined in a sandy beach by 50 experiments designed with CCD. The experiments are carried out in laboratory flume in Faculty of Civil and Environmental Engineering, Tarbiat Modares University with high accuracy. The experimental setup is designed to simulate varying beach groundwater level and SWL and course sand (d50=0.8mm) is selected for beach material. Analysis of hydrodynamic data of the experiments indicated that the type of breaking waves is plunging wave and the hydrodynamic status of the swash zone is intermediate condition. The starting position of swash sedimentation (SWS) is extracted from mean of the beach profiles evolution.By analyzing of experiments' SWS using CCD, a cubic model is suggested with %95 confidence level and predicted R-squared of 0.86. The results of model revealed that groundwater level has no significant effect on SWS. Wave height is the most influential factor affecting SWS and increasing wave height result to this position moves to upper beach rapidly. In addition, increasing beach slope causes the movement of SWS toward the beach. Increasing sea level lead to the displacement of SWS toward the sea.This model indicated that the effect of wave height on SWS depends on wave period strongly and there is significant interaction between them. In addition, there is slightly interaction between the SWL and wave height and these variables influence on the role of each other in SWS.},
Keywords = {sandy beaches,swash zone,Response surface method,laboratory model,starting position of swash sedimentation},
volume = {17},
Number = {3},
pages = {183-184},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1906-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1906-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Noori, Roohollah and Moazami, Saber and Salimian, Mohammad and Momeni, Mahmudrez},
title = {Evaluation of Support Vector Machine Performance for Carbon Monoxide Prediction},
abstract ={In Carbon monoxide (CO) is one of the main air pollutant parameters in the atmosphere of Tehran, Iran. Generally, it is difficult to predict and control CO concentration because it is essentially nonlinear time-varying system. Recently, in particular, environmental control such as CO concentration level control is regarded as one of the most important factors in environmental protections. This paper describes forecasting and more specifically uncertainty determination of CO concentration during the modeling process using a support vector machine (SVM) technique. Uncertainty of the air pollution modeling studies highly affected the simulation results. In this regards, it is very important to determine the uncertainty of air pollution models due to consequences on health of people exposed to the pollution. Therefore, this research aims to calibrate, verify, and also determine the uncertainty of support vector machine (SVM) in the process of air pollution modeling in the atmosphere of Tehran. To achive this goal, the SVM model was selected to predict arithmetic average of daily measured CO concentration in the atmosphere of Tehran. In this regards, the SVM model was calibrated and verified using six daily air pollutants include particulate matter with diameter equal or less than 10 micrometer (PM10), total hydrocarbons (THC), nitrogen oxides (NOx), methane (CH4), sulfur dioxide (SO2) and ozone (O3) and also six daily meteorological variables include pressure (Press), temperature (Temp), wind direction (WD), wind speed (WS) and relative humidity (Hum). The data was collected from Gholhak station located in the north of Tehran, Iran, during 2004-2005. Thereafter, the best developed SVM model for predicting the CO concentration was chosen based on determination of coefficient (R2). Finally, to determine the SVM uncertainty, the model was run many times with different calibration data. It led to many different results because of the model sensitivity to the selected calibration data. Then, the model uncertainty in the CO prediction process was evaluated using the width of uncertainty band (d-factor) and the percentage of measured data bracketed by the 95 percent prediction uncertainties (95PPU). Generally, the results confirmed the strong performance of the SVM model in predicting CO concentration in the atmosphere of Tehran. The predicted average daily CO concentrations by SVM model had a good agreement with the measured ones in the Gholahak air quality monitoring station. It was found that the determination of coefficient for calibration and validation of SVM model were equal to 0.89 and 0.88, respectively. Furthermore, the results indicated that the SVM model has an acceptable level of uncertainty in prediction of CO concentration in which the level of d-factor and the percentage of measured data bracketed by the 95PPU in the validation step were 0.74 and 76, respectively. Therefore, The obtained results indicated that the SVM model had an acceptable level of uncertainty in prediction of CO concentration. Therefore, it can be concluded that the SVM model is able to predict the CO concentration in the atmosphere of Tehran while it resulted an acceptable level of uncertainty. Finally, due to the proposed methodology is general, the authors suggest to apply it for analyzing the uncertainty of SVM model in other fields of science and engineering.},
Keywords = {Support vector machine,Air pollution,Uncertainty Analysis,Tehran,Carbon Monoxide},
volume = {17},
Number = {3},
pages = {195-202},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9875-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9875-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Mousavi, Seyed Roohollah},
title = {Strengthening of concrete
columns by near surface mounted method with different material bars and confined with CFRP sheet},
abstract ={In recent years, Fiber-reinforced polymer (FRP) materials are increasingly used for strengthening and retrofitting of reinforced concrete structures. Fiber-reinforced polymers in the form of jackets with the fibers typically in the columns’ circumferential direction, are quite effective in carrying shear and in providing confinement. In addition, the previous studies show that the FRP jacket can greatly enhance the dissipation capacity and ductility of reinforced concrete columns. However, FRP jackets are not effective for the strengthening of columns in flexure. To overcome difficulties associated with FRP jacketing, recent research efforts have focused on the use of near surface mounted (NSM) FRP or stainless steel reinforcement through a combination of externally bonded (EBR) FRP sheets and anchors for the flexural strengthening of columns. NSM strengthening technique consists of FRP rods embedded in grooves made on the surface of the concrete and bonded in place with epoxy. The NSM technique is not effective in terms of enhancing the energy dissipation capacity of RC columns. Therefore, by combining NSM technique with FRP confinement sheets, a high effective technique (hybrid FRP-based strengthening technique) can be obtained. FRP and steel bars have been used together for reinforcing the concrete beams in previous studies. However, the combination of both materials for strengthening of reinforced concrete columns is not common. The present paper experimentally investigates the effects of combined NSM-GFRP bars with the CFRP confinement sheets and also NSM-GFRP bars with NSM-Steel rods on strengthening of reinforced concrete columns. It should be noted that in combinatory method of NSM-GFRP with NSM-Steel, NSM-Steel to NSM-GFRP ratios is different. The experimental program includes five square columns with a cross section of 250*250 mm and the length of 1200 mm. The columns were tested to failure by applying constant axial compressive and cyclic lateral loading. According to the results, it is indicated that using these two combinatory reinforcing methods cause an increase in load capacity, ductility, dissipated energy and initial stiffness of columns compared to the control column and also columns reinforced by using NSM-GFRP bars. Furthermore, NSM-GFRP technique increases the load capacity 43 percent in comparison with the control specimen. In the case of combined retrofitting methods, load capacity increase was up to 60 percent. Also, using NSM-GFRP reinforcement causes 7 percent increase in ductility and 6 percent decrease in dissipation capacity. In contrast, in the specimens reinforced by the combinatory methods, the ductility parameter and dissipation capacity increase 3 to 150 percent and 24 to 133 percent, respectively. In addition, hysteretic diagrams corresponding to specimens strengthened by combinatory methods has less pinching effect than those of the control specimen. Experimental results indicate that the reinforced concrete column strengthened by combinatory method of NSM-GFRP with NSM-Steel is a viable solution toward enhancing the behavior of RC columns subjected to simultaneous axial and seismic loads. This is especially the case when the retrofitting scheme contains higher NSM-Steel to NSM-GFRP ratio. Finally, due to corrosion of steel reinforcement, NSM-GFRP bars combined with CFRP confining sheets is selected as the best choice of strengthening.},
Keywords = {NSM-Steel,NSM-GFRP,reinforced concrete,Strengthening,CFRP confinement,NSM-GFRP,NSM-Steel},
volume = {17},
Number = {3},
pages = {203-212},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-10569-en.html},
eprint = {http://journals.modares.ac.ir/article-16-10569-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {moludi, farzin and Kheyroddin, Ali and Hemmati, Ali},
title = {Investigation of the Seismic Behavior of Reinforced Concrete Beam-column Connections Made of High Performance Fiber Reinforced Cementitious Composites (HPFRCC)},
abstract ={Investigation of the Seismic Behavior of Reinforced Concrete Beam-column Connections Made of High Performance Fiber Reinforced Cementitious Composites (HPFRCC) In recent years, the use of the HPFRCC materials has been taken into consideration in order to construct safe structures against earthquake. High performance fiber reinforced cementitious composites (HPFRCC) refer to the materials, including cement mortar with fine aggregates and fibers. The distinctive feature of the materials is that they exhibit strain hardening behavior under tensile loading unlike normal concrete and fiber reinforced concrete. The HPFRCC materials can be used for seismic retrofitting of structural components, construction of structural fuses and in areas susceptible to degradation in structures, such as beam-column connections and shear wall interface beam. As the beam-column connections are considered as one of the points of damage in concrete flexural frames, the use of the HPFRCC materials in the beam-column connections, which have high strength and ductility, can lead to the formation of the structures with higher strength and ductility compared to the conventional concrete structures. This study first introduces the materials and then determines the effect of the use of the HPFRCC materials in the beam-column connection performance. Therefore, the results of laboratory studies conducted by Chao at University of Michigan were used to verify the finite element model. The effect of the different parameters of beam-column connection, including HPFRCC materials length area in the beam, HPFRCC materials length area in the column, compressive strength of concrete and HPFRCC materials, the distance between stirrups in the beam and the distance between stirrups in the column, individually or combined, and performance of connection were investigated in the base model. The results showed that maximum strength, yield strength and ductility ratio of beam-column connection, if the HPFRCC materials are used in some parts of the beam or column (with panel zone), are respectively 36.9%, 10.4% and 53.1% greater than the beam-column connection made of reinforced concrete. Furthermore, the concrete compressive strength parameter has a significant effect on the connection ductility ratio so that the ratio of ductility of the connection with 35 MPa concrete is 40.7% greater than the base connection (University of Michigan). It is notable that in the laboratory connection of the University of Michigan where the HPFRCC area length in the beam is twice the beam depth (711.2 mm), the reduction of the HPFRCC area length just in the beam led to the 40.7% increased ductility ratio of the connection from twice the beam depth (711.2 mm) to the length equal to the beam depth (355.6 mm) compared to the base connection (University of Michigan) while it had minimal effect on connection strength. Moreover, the use of the HPFRCC area just in the column led to the 50.1% increased ductility ratio of the connection compared to the base connection (University of Michigan). The results indicated that when HPFRCC materials were used in the beam, the use of the HPFRCC materials in the column did not have a significant effect on the strength and ductility ratio of the connection. Keywords: HPFRCC, Reinforced Concrete, Beam-Column connection, Seismic Behavior, Ductility.},
Keywords = {HPFRCC,HPFRCC,reinforced concrete,Beam-column connection,Seismic behavior,ductility},
volume = {17},
Number = {3},
pages = {213-226},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-934-en.html},
eprint = {http://journals.modares.ac.ir/article-16-934-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {raji, mahdieh and Mirbagheri, Seyed Ahm},
title = {Effects of return mixed liquor recycling ratio on A2/O process},
abstract ={Discharging wastewater effluent to surface water or groundwater is so dangerous for environment, while it includes nutrient. As the phosphorus and nitrogen combinations in the aquatic environments have harmful impacts (mainly the poisonousness of ammonia, overgrowth of aquatic plants, groundwater pollute to nitrate and diseases caused by drinking the polluted water, and also eutrophication, resulting in frequent outbreaks of algal blooms and threatening the reliable supply of drinking water resources), some limitations were imposed on the consistency of these combinations in the entry waste. So nowadays removal of these combinations must be considered in designing of the treatment plants and also systems designed for treating the municipal wastewater must be able to remove nitrogen and phosphorus combinations to reach the standard limit. Therefore, in order to good performance of the aerobic-anaerobic A2/O method, it is proposed in this research and a study in advanced treatment of municipal wastewater using the A2/O method to remove nitrogen and phosphorus in the pilot scale in Ekbatan WWTP has been done. In this research, firstly the principals of biological removal of nitrogen and phosphorus, and secondly the basis of designing biological treatment plants have been investigated. Then for laboratorial studies, an A2/O pilot has been made. This pilot consists of anaerobic, anoxic and aeration tanks and also sedimentation tank. The volume of these 4 tanks are 40, 60, 170 and 120 L, respectively. In order to simulate the real condition, this pilot has been set up in Ekbatan plant and the experiments were done to observe the effect of hydraulic residence time on nitrate, ammonia and phosphorus removal and also the effect of oxic mixed liquor recycling ratio on nitrate removal has been conducted. In order to observe the nitrate, ammonia and phosphorus removal process efficiency, the experiments were done in a period of three months and in 5 aeration hydraulic residence times, 4, 6, 8, 10 and 12 hours. In these experiments, the returned sludge was 25% and the oxic mixed liquor recycling ratio was 75%. After determining the best hydraulic residence time, experiments continued in 5 different oxic mixed liquor recycling ratios, 75%,150%, 225%, 300% and 375%. It was concluded that at aeration hydraulic residence time of 8 hours, 96% COD , 95% ammonia and 79% phosphorus (effluent: 9 mg/L COD, 0.87 mg/L ammonia, 2.1 mg/L phosphorus, 18.7 mg/L nitrate) removal were achieved and that was the best HRT. Furthermore, according to the mixed liquor recycling ratio experiments, when the oxic mixed liquor recycling ratio was about 180 - 200%, optimum removing nitrate has been occurred. Although the mixed liquor recycling ratio of 225 - 275% resulted better efficiency for nitrate removal, it is not proposed, because effluent limitations in Iran for the nitrate is up to 10 mg/l which it is resulted in the mixed liquor recycling ratio of 180 -200%, and the other reason is that, with increasing the oxic mixed liquor recycling ratio, energy costs will increase, too.},
Keywords = {A2/O,ammonia,Nitrate,Phosphorous,A2/O process,mixed liquor},
volume = {17},
Number = {3},
pages = {227-234},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8150-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8150-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Naseri, Mohsen and Erfani, Saee},
title = {Evaluation of Effective Parameters on the Axial Load Carrying Capacity of Preloaded Strengthened Steel Box Columns},
abstract ={Strengthening of existing structures is one of the most important issues in the field of structural engineering. Due to avoiding any interruption of service on a structure and economic issues, strengthening process usually occurs when a member is under service loads. On the other hand in the loaded steel columns, it is really difficult to weld plates after unloading the column from existing loads, Therefore one of the important issues being neglected in the redesign process of strengthened columns is the significant axial load existing in the column, caused by service loads before strengthening them. This paper aims at numerically investigating the behavior and ultimate load bearing capacity of in-service strengthened steel box columns with continuous welded plates. Effects of different parameters on the capacity of preloaded strengthened columns are presented and discussed. Included in the result are the effects of initial imperfection; magnitude of preload before strengthening; slenderness ratio of the strengthened column and ratio between cross sectional area of reinforcing plate and unstrengthened column. To investigate the effect of these parameters, each un-retrofitted specimen is exposed to the preloading levels of 0.0, 0.2, 0.4 and 0.6 of the load carrying capacity of unstrengthened column. Then results of this preliminary analysis are defined as a predefined field for the column of same retrofitted model and ultimate bearing capacity of the strengthened model is calculated using a modified Riks analysis method. The critical load carrying capacity of models without pre-existing axial load was set to the theoretical value presented in ANSI/AISC 360-10 and suitable imperfection for each model was calculated. This is because the main objective of this study is the variation of results with respect to the existing design curves. Based on the results of numerical analysis, application of preload to unstrengthened column magnifies the initial geometric imperfection of the column and consequently decreases the ultimate bearing capacity of strengthened column. Also as the magnitude of axial load existing prior to addition of reinforcing plates increases, the ultimate bearing capacity of the strengthened column decreases with respect to the calculated theoretical value. The maximum amount of this reduction for the preload ratios of 0.2, 0.4 and 0.6, is respectively up to 2%, 5% and 9.5% of the load-bearing capacity of strengthened column. As another result, slenderness ratio is one of the main parameters that affect the bearing capacity of specimens with a specified preload level. This means that at a constant preload level the maximum reduction in bearing capacity occurs for models with median slenderness ratio. Also models with cross sectional ratio of reinforcing plates ranging from 0.4 to 1.0 were studied and it was shown that inside this range the cross sectional ratio of reinforcing plates parameter does not have remarkable effect on the ultimate bearing capacity of column. At the end, an empirical relation is proposed to calculate reduction of ultimate bearing capacity for columns with different slenderness ratios and preload level. Results of this study may be utilized to increase the accuracy of redesigning process during in-service strengthening of steel box columns.},
Keywords = {Strengthening,Load Carrying Capacity,preload,Steel box column},
volume = {17},
Number = {3},
pages = {235-246},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12167-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12167-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {yazdani, mahdi},
title = {Sensitive Analysis of Nodal Force Function in the Elastostatic Problems in Decoupled Equations Method},
abstract ={The elastostatic problems are a significant subject in the analysis and design of solids and structures. As most of the complicated elastostatic problems do not have closed-form solutions, numerical methods such as finite element method (FEM), boundary element method (BEM), discrete element method (DEM), meshless methods, scaled boundary finite element method (SBFEM), and hybrid methods are the current approaches dealing with these types of engineering problems. This study presents a novel application of the decoupled equations method (DEM) to assessment elastostatic issues. In the present method, the so-called local coordinate's origin (LCO) is selected at a point, from which the entire domain boundary may be observed. For the bounded domains, the LCO may be chosen on the boundary or inside the domain. Furthermore, only the boundaries which are visible from the LCO need to be discretized, while other remaining boundaries passing through the LCO are not required to be discretized. In this method, only the boundaries of problems are discretized using specific higher-order sub-parametric elements and higher-order Chebyshev mapping functions. Implementing the weighted residual method and using Clenshaw-Curtis quadrature result in diagonal Euler’s differential equations. So, the coefficient matrices are diagonal, which provide a system of single Euler’s differential equations for the ith degree of freedom (DOF). If n indicates the number of DOFs of the problem assumed to be analyzed by the proposed method, only n Euler’s differential equations (with only one unknown differential equation for each DOF) should be solved. In the proposed method, the LCO is the same for all nodes, for which the LCO has the same displacement components. Therefore, the physical concept of this fact may be considered as some semi-parallel springs adjoining to each other at the LCO. Therefore, the proposed procedure is called “redistribution” of the stresses in the present method. At the final step, using the calculated displacement field along ξ, the displacement at any point of the problem’s domain is interpolated by using the proposed special shape functions. Although the governing equation of each DOF is decoupled from those of other DOFs, however the “redistribution” of the stresses at the LCO and resolving the problem for each DOF, represents the connection between all DOFs of the domain. In the solution procedure, the order of displacement function u(ξ) depends on nodal force function F^b (ξ). To analysis of elastostatic problems in the classical Decoupled Equations Method, F^b (ξ) varies in the undertaken domain like a body force. Therefore, F^b (ξ) is defined as a linear function. In this study by proposing new forms of force function, the response of elastostatic problems is assessed. In the following Sensitivity of this method via proposed nodal force functions is fully demonstrated through two benchmark problems. The results show that stress and displacement fields totally depend on the form of force function. Also, the results show to get optimum results, proposing an appropriate nodal force function corresponding to physical concept is necessary. For example in the cantilever beam which is subjected to a shear force at its free end, by considering the linear form for nodal force function results in minimum error. In the other hands, in the Kirsch’s problem with a central small circular hole, considering the nonlinear form for nodal force function leads to minimum error.},
Keywords = {Decoupled equations method (DEM),elastostatic problems,redistribution stress,nodal force function,2D Problems},
volume = {17},
Number = {3},
pages = {247-257},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1504-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1504-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Construction and evaluation of damage detection concrete sensor consistent with concrete pavement},
abstract ={Annually, various concrete infrastructures are damaged and may collapse due to the presence of destructive factors. In this regard, the Structural Health Monitoring (SHM) provides a way to evaluate the safety and durability of a structure during its service life in order to ensure the serviceability and sustainability of it. Therefore, the sensor technology is a critical part to operate SHM system for recording of relevant data through its lifespan. Sensor is a device which is capable of identifying the probability or the value of parametric changes and showing them as a relevant output (typically electrical or optical signal. Making materials electrically conductive may be useful in many different ways such as creating piezoresistive sensors with the ability to acquire stress-strain or load-displacement data or creating sensors with the ability to acquire data on the extent of damage to the concrete. The piezoresistive sensor is capable of detecting the applied forces to the structure based on the changes in the electrical resistance. But the damage detection sensor operates based on the contacting conduction of CNTs. This means that by increasing the amount of CNTs in concrete, the three-dimensional contacting network of CNTs is built. When the amount of CNTs exceeds the percolation threshold, the contacting conduction will affect the electrical conduction of nanocomposites. One of the most significant and economical types of the sensor is the damage detection sensor which is provided by mixing conductive fibers (such as carbon nanotubes (CNT)) with concrete. For preparing damage detection sensor, CNTs and surfactants were mixed in the water for 10 minutes using a magnetism stirrer at 5000 rpm. Then, the mix was prepared at one ultrasonic dispersion energy. Then the cement and CNTs were added to high-speed mixer to be uniformly mixed. After adding the aggregate to the mixer, the concrete was placed in pre-oiled molds and by applying appropriate vibration, any air that may have been trapped was released. The specimens were curing for 28 dayes and they were tested under the static loading by Instron-Tech. test equipment. In order to remove the effect of polarization which is due to the movement of free ions in the concrete sensor during the measurement, an alternating current generator with the magnitude was used to nullify this phenomenon. After preparing the sensors, two main factors affecting the performance of concrete sensors are the amount of CNTs and their dispersion quality in the mixture. The goal of this study is to determine the optimum amount of CNTs with regard to the combined effects of the surfactant and the CNTs dispersion quality on the performance of the sensor using various criteria such as sensitivity of the sensor (Se), the standard deviation of the prediction error as electrical criteria and comparison and flexural strength as mechanical critera. The results have demonstrated that the sensor provided by 0.15 wt% CNTs, superplasticizer and SDS as a surfactant has the best performance. Also, The static criteria indicated that the quality of the dispersion (using proper surfactant material) and the amount of CNTs are effective on the sensitivity and the standard deviation of the prediction error, respectively.},
Keywords = {Concrete sensor,Carbon nanotubes,mechanical properties,Electrical properties,concrete},
volume = {17},
Number = {2},
pages = {1-9},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4295-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4295-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Ayati, Bit},
title = {Reactive yellow 81 removal using photocatalytic cascade disk reactor coated by ZnO nanoparticles},
abstract ={The use of different synthetic dyes in textile industries has increased in recent decay, resulting in the release of dye-containing industrial effluents into natural aquatic ecosystem. Since most of dyes are usually very recalcitrant to microbial degradation, therefore dye removal from effluent is a main concern in many studies. Different process was used for the treatment of dye effluent. In the last few years, studies were focused on advanced oxidation process (AOPs) methods such as UV-ZnO, UV-H2O2, UV-O3 and UV-TiO2. Photocatalytic process such as UV-ZnO is an efficient method that treats non-degradable wastewater by active radicals. The photocatalysis needs a photo-reactor that contacts reactant, products and light. In recent years, different types of photo-reactors have been used for wastewater treatment. In some reactors, nano-photocatalysts are utilized in slurry form, and the other particles are coated on bed. In Photocatalytic reactors with fixed bed, nano-photocatalysts are immobilized on bed and do not need the separation unit, but the main disadvantage of this photo-reactors is the low mass transfer rate between wastewater and nano-photocatalysts. Consequently, Different optimal photo-reactors were developed for increasing mass transfer rate. In this study, a novel photocatalytic cascade disc reactor coated with ZnO nano-photocatalysts was applied and in order to increase mass transfer rate artificial roughness were created on the surface of disks. Applying artificial roughness changes mass transfer rate by providing vertical mixing, creating secondary currents and increasing the Reynolds number. This photo-reactor has a number of advantages that include eliminating the need for catalyst separation units as the catalyst is immobilized, creating the ﬂow mixing by non-mechanical method, increasing the transport of oxygen from the gas phase to the photocatalyst surface by providing the flow cascade pattern. The photo-reactor was used in order to remove Reactive Yellow 81 (RY81) dye from textile industry effluent, by means of UV-ZnO process. RY81 is a reactive dye composed of 10 Benzene rings and two –N=N azo bonds. The effect of different operational parameters such as initial Concentration of dye, pH, Catalyst surface loading and flow rate in removal efficiency was investigated, and the optimal value of those parameters were 50 mg/L, 8, 40 gr/m2 and 80 cc/s, respectively. A rate equation for the removal of RY81 was obtained by mathematical kinetic modeling. The Langmuir-Hinshelwood kinetic model is one of the most common kinetic models that are used for studying the kinetics of heterogeneous photo-catalysis. The results of reaction kinetic modeling indicate the conformity of removal kinetics with Langmuir-Hinshelwood model, and the constants kL-H and Kads were obtained 7.17 mg L-1 hr-1, 0.122 mg-1 L, respectively. One way of inserting various operational parameters to a rate equation is regression analysis. Therefore, in this study, nonlinear regression model was developed for prediction pseudo- first order rate constant as a function of initial concentration of dye, pH, catalyst surface loading and flow rate. This equation could properly predict (R2=0.95) the removal rate constant of RY81 removal in the photocatalytic cascade disk reactor under different operational conditions and a good consistency was observed between the calculated results and experimental findings.},
Keywords = {Reactive Yellow 81,Non-linear regression,Cascade photocatalytic reactor,Langmuir-Hinshelwood},
volume = {17},
Number = {2},
pages = {11-20},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11565-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11565-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {AminAfshar, Maij},
title = {Improvement in seismic control of frame structures against far-fault and near-fault earthquakes with new strategy of Gaussian linear optimal control},
abstract ={In this paper, a modified linear-quadratic-Gaussian (MLQG) optimal control algorithm is proposed for controlling the seismic response of frame structures. Environmental loads (e.g., earthquakes) at the moment of calculation and exertion of control forces to structures, can not be measured. So these loads are not included in the conventional control algorithms, such as linear quadratic regulator and linear-quadratic-Gaussian control. Therefore the command of LQG optimal controller is merely a proportional feedback of estimated state of structure at the moment of exertion. This state approximation is performed by optimal state stimator or Kalman filter. In the proposed control algorithm, using a new variable, including control force andearthquake force, acceleration of gound motion, which is non-measurable duting exertion of control force, is considered in the state space equation of motion and also in both of Kalman Filter estimator and the optimal regulator. According to the proposed control algorithm, two ways are selected. So first command control are sum of the control force and ratios of the estimated state and measurement output of sensors, which are obtained and used in previous time step. The estimated state of system, used in the first command control, is calculated by the conventional and knownKalman Filter. but in second strategy of control, First, the Kalman Filter estimator is modified based on new state space equations, and then the estimated state of structure obtained from it, is used for calculation of command control. Numerical simulation of a seven-storey structure with active control system under several far-fault and near-fault earthquakes are performed to show effectiveness of two proposed controls on mitigation of structural responses and compare to those of a uncontrolled structure and a structure controlled with conventional control. Also sensitivity of some perforemance measures for controllers are investigated against changes of some controlling and perturbation parameters of systems or uncertainties. The alalysis results demonstrate that control performance of the proposed controllers, specially the second one, are better and also stable and robust under variations of uncertainties. So that the greatest reduction in maximum displacement (even up to 80 percent) compared to uncontrolled displacement of structure and meanwhile, very low energy consumption are attained by the second proposed control strategy.but in second strategy of control, First, the Kalman Filter estimator is modified based on new state space equations, and then the estimated state of structure obtained from it, is used for calculation of command control. Numerical simulation of a seven-storey structure with active control system under several far-fault and near-fault earthquakes are performed to show effectiveness of two proposed controls on mitigation of structural responses and compare to those of a uncontrolled structure and a structure controlled with conventional control. Also sensitivity of some perforemance measures for controllers are investigated against changes of some controlling and perturbation parameters of systems or uncertainties. The alalysis results demonstrate that control performance of the proposed controllers, specially the second one, are better and also stable and robust under variations of uncertainties. So that the greatest reduction in maximum displacement (even up to 80 percent) compared to uncontrolled displacement of structure and meanwhile, very low energy consumption are attained by the second proposed control strategy.},
Keywords = {LQG optimal control,Kalman filter,Active structural control,Structural dynamics,Earthquake},
volume = {17},
Number = {2},
pages = {21-33},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9795-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9795-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Turbulence analysis around high buildings during the construction period with different forms in plan},
abstract ={Development in engineering knowledge, methods and techniques in the construction industry has provided the possibility of establishing structures that are significantly light, high and flexible. The sensitivity of high buildings against wind power is more than other ordinary buildings. Basically, wind power has an important role in the design of high buildings. Therefore, it is essential to study more carefully the effects of wind forces in the design of these structures. An important issue that must be considered in all tall building studies in the field of wind engineering is study of atmospheric boundary layer around the structures. Atmospheric boundary layer is a layer of air around the surface of the earth that at a height above the earth surface, friction has not effect on the natural flow of wind. In the present experimental research a wind tunnel was used. It generally consisted of a huge duct in collaboration with a fan in the middle. By switching on the fan, air blows into the duct. Different measurement devices were installed along the wind tunnel which made it possible to consider different test sections in width, height and longitude. In the present research a wind tunnel with 2 meter long, 1.2 meter height and 1 meter width was used with an open wind circulation system. To check every structure in the wind tunnel environment at first the atmospheric boundary in that environment should be simulated. After this stage, any structure can be placed in a wind tunnel and be examined. In this study, two buildings with the same height and cross sectional area but different in plan were examined experimentally. Both Buildings were modeled with scale of 1:600 as a fifteen floors structure with twenty cm height. Buildings had square and circular plans. Speed, pressure and turbulence at any point of the tunnel test section can be measured directly. In this study the rate of percentage of turbulence is provided in different parts of the front and back of the building. In the recent years, numerical models specially finite volume methods have been developed in the fluid sciences. In the present research, all models were simulated in Fluent software numerically. A comparison between numerical and experimental data could help one to see the ability of numerical models. Moreover, by using the numerical model many points which are not accessible in the experimental model can be recorded and analyzed. In different sides of each model the turbulence percent was measured and analyzed. Results showed that by increasing the side walls the percent of turbulence increased. The reason can be more effect of wind impact on the building surface which caused to increase the friction meaningfully. It was also concluded that covering the ground surface around the considered tall building with canopy and trees or other buildings caused more percent of turbulence. It was also observed that from a certain height of building to up, the turbulence percent was went to zero which means non friction along the wind towards the structure. The results of this study helps to provide a better understanding of the effect of plan shape of a tall building in view of wind impact.},
Keywords = {Wind tunnel,Percent of Turbulence,Tall Building,Canopy,Fluent},
volume = {17},
Number = {2},
pages = {33-45},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1741-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1741-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {khatibinia, mohse},
title = {Seismic performance assessment of concrete beam–column connection strengthened Carbon Fiber Reinforced Polimer},
abstract ={In the design process of a moment resisting frame (MRF), the principle of weak–beam and strong–column should been considered because the plastic hinge occurs in the beams. This mechanism is caused that the frame has capable of dissipating significant energy and remain stable in the inelastic region. Hence, the stability is defined as the ability of the frame to maintain its elastic level of resistance throughout the entire inelastic range of response. Using this principle, plastic hinges can be develop in the beams adjacent to the connections and usually very close to the column face. This mechanism allow cracks caused by the plastic hinging. The cracks can also propagate into the connection core region, and initiate a brittle failure mechanism. Furthermore, the mechanism has been not established in many existing MRFs designed based on the previous codes. Hence, the methods have been proposed and developed in order to relocate the plastic hinge away from the column face. Fiber Reinforced Polymer (FRP) has been used as a strengthening solution of beam–column connections and successfully reported for retrofitting existing structures. In fact, the use of a web–bonded FRP retrofitting system can control the mechanism of plastic hing and provide the strong–column weak–beam concept. Due to the many advantages, such as high strength, low weight, endurance and convenience, Carbon Fiber–Reinforced Polimers (CFRPs) have been widely used in strengthening concrete structures. However, the strength and stiffness of CFRP are severely reduced at elevated temperatures, which will affect the strengthening effect seriously. In this study, six schemes of strengthened concrete beam–column connection using CFRP are proposed and the seismic performance of the strengthened connection is investigated. In order to achieve this purpose, seven scaled–down RC exterior joint of a typical ordinary MRF are chosen and modeling this strengthened connection is implemented in the general finite element program, ABAQUS software. In the finite element model of strengthened concrete beam–column connection, the concrete is modeled using the damaged plastic model. The sheets of CFRP are also considered as the elastic and orthotropic model. These schemes of strengthened concrete beam–column connection are tested under moderately monotonic/cyclic loads. In order to verify the finite element model of the connection, the analysis results of this model is compared with the experimental investigation on the external beam–column connection repaired strengthened using CFRP. The results demonstrates the verification of the finite element model. The selection of the best scheme of strengthened concrete beam–column connection using CFRP is based on the improvement of the seismic performance of connection such as the load–carrying capacity, the energy absorption, the initial stiffness and changing failure mechanism of connection. The nonlinear results show that the proper layout of CFRP sheets can increase the load–carrying capacity, the energy absorption and the initial stiffness of connections. Furthermore, the proposed schemes of strengthened concrete beam–column connection are caused that the failure is relocated from the column face and located in beam. Therefore, the proposed best scheme of strengthened concrete beam–column connection using CFRP can be recommended and utilized in the practical projects of concrete structures.},
Keywords = {beam–column connection,strengthening connection,Carbon Fiber Reinforced Polimer,Improvement of seismic performance},
volume = {17},
Number = {2},
pages = {45-55},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7273-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7273-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {shakerkhatibi, mohamm},
title = {Performance evaluation of Tabriz petrochemical wastewater treatment plant},
abstract ={Introduction: Petrochemical industry is one of the major industries playing significant role in the economy of Iran. In general, petrochemical effluents contain various contaminants including suspended solids, organic matters, oil and grease, metal salts, sulfide, ammonia, hydrocarbons, cyanides, volatile organic compounds (VOCs) and other toxic substances. In most of petrochemical complexes, wastewaters are treated by activated sludge process along with the oil/water separation systems as a pretreatment. Since the performance evaluation of wastewater treatment plant is required to assess the effluent quality, to meet higher treatment requirement and to know the feasibility of handling higher hydraulic and/or organic loadings, this study was conducted to evaluate the performance of a full-scale petrochemical wastewater treatment plant. Materials and methods: Wastewater treatment system consists of a screening unit, an API, an equalization basin, coagulation and flocculation, DAF system, aeration tanks, primary and secondary clarifier and filtration. The treatment plant was designed to treat the wastewater generated from different units of petrochemical complex with reuse purposes of treated effluent. To evaluate the performance of the treatment plant, 12-h composite flow weighted samples were carried out in 4 days within 6 month and were analyzed for COD, BOD5, TDS, TSS, phenol, cyanide, oil, ammonia and TKN in accordance to standard methods. Microbial structure of activated sludge was also evaluated. Overall performance of the plant and the performance efficiency of each unit were calculated. Results: According to the results, the actual average influent flow was significantly lower than the average design flow based on the long-term data and our measurements. This increases the hydraulic retention time (HRT) in all units in the WWTP. Based on the results, the values of COD, BOD5 and TSS in the influent and effluent were 1319±230, 967±491 and 227±174 mg/l and 73.6±19.6, 33.6±25.9 and 6.4±5.9 mg/l respectively. The ratio of BOD5/COD was calculated about 0.58 indicates a good potential for biodegradability of the wastewater. The results also revealed that 68.5% removal of COD and 81.9% removal of BOD5 have been occurred in preliminary and primary units while; these units are usually designed for the elimination of oil and suspended solids as well as the equalization of quantitative and qualitative parameters of the influent. At an organic loading of 0.48±0.15 kg/m3.d the removal efficiencies for COD and BOD5 in biological unit were calculated about 37 and 46% respectively. The mean value of MLSS within the biological reactor was 1463 mg/l. In addition, the mean plus standard deviation values of MLSS measured in returned activated sludge (RAS) were 2323 ± 1080 mg/l. According to the daily average concentrations of COD in the effluent of the WWTP, in some cases within the study period, the COD values were exceeded from national discharge standards. Microbial analysis showed that among the isolated bacterial strains, the genus belonging to Alcaligenes, Pseudomonas, Bacillus and Moraxella as heterotrophic nitrifying bacteria was identified as predominant strains in biological unit. Conclusion: Based on the results, in 64% of our measurements (135 days from 209 days of study period), the daily average effluent COD values were above national guidelines for surface water discharge (60 mg/l). In 3% of the time during the study period, the daily average values of COD in the effluent were more than 200 mg/l. The results also indicated that the average effluent concentration of oil was significantly higher than the expected design value.},
Keywords = {Performance Evaluation,Petrochemical industry,Activated sludge,Wastewater treatment,Microbial analysis},
volume = {17},
Number = {2},
pages = {55-67},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8572-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8572-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Hajnorouzi, Mohamad Mehdi},
title = {FINITE ELEMENT ANALYSIS OF BURIED PIPELINES CROSSING REVERSE FAULT},
abstract ={Response evaluation of buried steel pipelines at active fault crossings is among the top seismic design priorities. This is because the axial and bending strains induced to the pipeline by step-like permanent ground deformation may become fairly large and lead to rupture, either due to tension or due to buckling. Surface faulting has accounted for many pipe breaks during past earthquakes, such as the 1971 San Fernando (USA), the 1995 Kobe (Japan), the 1999 Izmit (Turkey), the 1999 Chi-Chi (Taiwan) events and more recently, the 2004 Mid Niigata earthquake in Japan. Literature review suggests that previous researches in the analysis of pipeline subjected to fault motion have been mainly focused on the case of strike-slip fault. Certainly, a 3D large scale finite element analysis is a powerful method and allows a rigorous solution of the problem with minimizing the number of necessary approximations. The aim of present work is to examine and compare the mechanical response of continuous (welded) buried steel pipelines crossing active reverse faults by three dimensional FEM. General-purpose ﬁnite element program ABAQUS is employed to simulate accurately the mechanical behaviour of the steel pipe, the surrounding soil medium and their interaction, considering the non-linear geometry of the soil and the pipe through a large-strain description of the pipeline-soil system and the inelastic material behaviour for both the pipe and the soil. For 3D FEM continuum model, an elongated prismatic model is considered, where the pipeline is embedded in the soil. Four-node reduced-integration shell elements (type S4R) are employed for modeling the pipeline cylinder, whereas eight-node reduced-integration brick elements (C3D8R) are used to simulate the surrounding soil. The analysis is conducted in two steps; gravity loading is applied ﬁrst and subsequently fault movement is imposed. Seismic fault plane is assumed to be located at the middle cross-section of the pipeline. The steel pipeline was of the API5L-X65 type, with a bi-linear elasto-plastic stress–strain curve given by Ramberg-Osgood model. The mechanical behavior of soil material is described through an elastic–perfectly plastic Drucker-Prager constitutive model. A contact algorithm is considered to simulate rigorously soil–pipeline interaction which accounts for large strains and displacements. The analysis proceeds using a displacement-controlled scheme, which increases gradually the fault displacement. Quasi-static analyses were carried out by applying fault offset components to soil block in the continuum FE models through a smooth loading function of time. Buried steel pipelines have been analyzed for reverse fault motion to study the influence of design parameters viz. crossing angle, backfill properties, burial depth, pipe surface property, pipe material and cross-section properties on maximum compressive strain, and buckling of the pipeline. The following main conclusions were obtained based on the studied response of pipeline subjected to reverse fault motion using the FEM model. - For the steel pipeline subjected to reverse fault motion, compressive strain was always found to be more critical than the tensile strain. - The capacity of the buried pipeline to accommodate the reverse fault offset could be increased by adopting: a loose granular backfill, a shallower burial depth, near-parallel orientation with respect to the fault line, a smooth and hard surface coating, and increasing pipe-wall thickness. - Finally, the obtained information can provide either guidance for developing improved earthquake-resistant design or countermeasures to mitigate damage to pipelines crossing active reverse faults.},
Keywords = {Soil-pipe interaction,FEM,Reverse fault,Performance,Non-Linear Analysis},
volume = {17},
Number = {2},
pages = {67-80},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6953-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6953-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Evaluating of two phase models for numerical Simulation of sediment transport in a 180 degree Bend with lateral intake},
abstract ={A large number of flows encountered in nature and technology are a mixture of phases. Advances in computational fluid mechanics have provided the basis for further insight into the dynamics of multiphase flows. Currently there are two approaches for the numerical calculation of multiphase flows: the Euler-Euler approach and the Euler-Lagrange approach In the Euler-Euler approach, the different phases are treated mathematically as interpenetrating continua. In FLUENT, three different Euler-Euler multiphase models are available: the volume of fluid (VOF) model, the mixture model, and the Eulerian model. For sedimentation, we must use the Eulerian model. The Eulerian multiphase model in FLUENT allows for the modeling of multiple separate, yet interacting phases. The phases can be liquids, gases, or solids in nearly any combination. The Lagrangian discrete phase model (DPM) in FLUENT follows the Euler-Lagrange approach. The fluid phase is treated as a continuum by solving the time-averaged Navier-Stokes equations, while the dispersed phase is solved by tracking a large number of particles through the calculated flow field. Sediment transport by fluid flow is one of the most important two phase flow in the nature. Due to existence of secondary current in channel bends, the mechanism of flow and sediment transport in these channels is much complex and locationg lateral intake at outer bank of the bens decreases this compelexity. In this paper, mechanisms of sediments transport into the intake in a 180 degree bend channel with lateral intake have been simulated whit the Eulerian and Discrete phases models in fluent software. The intake is located at the outer bank of an 180o bend at position 115° with 45° diversion angle. The effect of diversion discharge rate and diversion angle on mechanism of sediment entry to the intake was considered. The turbulence model is k-ε model. Model҆s in different time has performed and the result compared with laboratory result.The results show in Qr=40%, the mechanism of sediment entry was consist of continues entrance from downstream edge of intake and periodic entrance from upstream of the intake, however in Qr=25%, the mechanism of sediment entry was only consist of continues entrance from downstream edge of intake. The two models (Eulerian and Discrete phases) have shown good results. The rout mean square errors for outer boundary of the path of the particle at the channel ҆s bed for two discharges (25% and 40%) have measured. The number of particle in discrete phases is limited; therefore this model cannot be display the depth of sediment. The Eulerian model displays the bed topography very well. Measuring mean square errors show that the model operation for topography simulation is very well. This model shows the location of intermittent dune and location of sediment accumulation very well. The discrete phase model can be shown the particle trapped place better than the Eulerian model. Due to increase in intake discharge, dimension of sediment accumulation is decrease. the mechanism of sediment entry to lateral intake is affected by diversion angle of intake. the minimum sediment is entered to lateral intake at diversion angle equal to 50 degree.},
Keywords = {Eulerian model,Discrete Phase Model,Bed topography,sediment transport,Fluent},
volume = {17},
Number = {2},
pages = {81-92},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12371-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12371-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Kholoosi, Mohammad Mehdi and RaeesiEstabragh, Ali and Abdollahi, Jamal},
title = {Effect of Cement on Geotechnical Properties of Hydrocarbon-Contaminated clay soil},
abstract ={Soil pollution by hydrocarbon is a significant Geo-Environmental problem that can affect the environmental quality of soil, groundwater and air. Soil can be contaminated by organic materials attributable to leakage from underground or aboveground storage tanks and accidental spills. The response of soil to the contaminants not only depends on the local environment but it is also influenced by factors such as particle size, bonding characteristics among particles, and ion exchange capacity. The transport of contaminant components from soil into groundwater can cause serious problems. The use of contaminated soil and its stabilization can be considered in earthworks such as embankments, backfills, and roads if there is no pathway for leaching of contaminants to underground water or if the contaminants pose no risk to the public and the environment. In some areas the native soil is contaminated with hydrocarbon substances. For performing projects in such areas, because of the haulage distance to suitable soil and economic considerations, often the use of local soil is dictated for construction. Thus, the treatment and stabilization of local soil must be considered. On the other hand, in some areas where the soil has been contaminated and the treatment is not economic, for the design of a project in these areas the effect of the contaminating substance on the soil behavior should be evaluated. Therefore, understanding the mechanical behavior of contaminated soils and their treatment is important. Improving the mechanical behavior of clay soils by stabilization is a means of fulfilling geotechnical design criteria. An investigation into the behavior of a contaminated clay soil with Anthracene and its treatment was carried out through a program of experimental tests.. Anthracene is a representative of one group of hydrocarbon, which are called PAHs (Poly Aromatic Hydrocarbons). PAHs create due to incomplete combustion of fossil fuels or wastes. In order to investigate the effect of cement on the stabilization of clay contaminated soil with Anthracene, the specimens of natural clay soil, contaminated soil with Anthracene, soil-cement and Anthracene-contaminated that is stabilized with different percentage of cement (5, 10, 15 and 20%) in different curing times (3, 7, 14 and 28 days) was prepared by static compaction method at maximum dry density and optimum moisture. Atterberg limits and Unconfined compressive strength (UCS) tests were conducted on the specimens. The results of the experimental work showed that adding Anthracene to clay soil, change the compaction parameters, for example, the dry specific weight of soil is reduced and the optimum water content is increased. Although, adding cement to the Anthracene-contaminated soil, improves the compaction of soil, it increases the dry specific weight and reduced the optimum water content. In addition, adding the Anthracene also is changed the unconfined compressive strength of soil, it reduces strength of soil. Although, adding cement is incresed the strength of the contaminated soil. The amount of increase in the strength is depended on the percent of cement and curing. The results showed that Atterberg limits are increased by adding Anthracene to the clay soil, but are reduced by adding Anthracene or cement or adding Anthracene to soil-cement. The results indicated that adding the Anthracene to the soil, changes its structure to flocculated shape, but the decreasing of friction between soil particles due to adding Anthracene, led the soil particles to move easily together. By the way, the results of this research showed that the cement could stabilize contaminated soil with Antracene.},
Keywords = {Atterberg Limits,Curing time,Flocculation,Elastic modulus},
volume = {17},
Number = {2},
pages = {93-106},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5946-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5946-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Hosseinzadeh, seyed ali asghar and Kamraninejad, ayub},
title = {Effect Of Slenderness Ratio On Nonlinear-Static/Cyclic Behavior Characteristics Of Shear Panels},
abstract ={Thin-walled structures are widely used in different engineering applications. Bridge and building plate girders, box columns and girders, frame bracing systems, liquid and gas containment structures, shelters, offshore structures, ship structures, slabs, hot-rolled W-shape steel profiles, steel plate shear wall systems and many other naval and aeronautical structures are examples of engineering elements that according to their applications use plate of various thicknesses. The knowledge of the actual behavior of plates in such structures can be, of course, helpful in understanding the overall behavior of the structures. In general, plates in thin-walled structures may be under various types of loading, such as shear loading. Material yielding and geometrical buckling of plates are two independent phenomena which may well interact with each other in shear panels. Depending on the material properties, slenderness and aspect ratios, and boundary conditions of perfectly flat plates, yielding may occur before, after or at the same time as buckling. Buckling in slender plates is a local and sudden phenomenon followed by large out-of-plane displacements and loss of stiffness. Slender plates are capable of carrying considerable post-buckling additional loads due to stresses in the inclined tension fields. On the other hand, a plate with low slenderness ratio yields before buckles and thus, no post-buckling capacity is expected. In between, in plates with moderate slenderness ratios, material yielding and geometrical nonlinearity happen almost at the same time. In the present paper, the behavior characteristics of shear panels with simple or clamed boundary conditions and three different materials (carbon steel, stainless steel and aluminum) are studied for various plate slenderness ratios, using finite element method. Results of nonlinear static analyses of different shear panels show that slender plates, depending on the slenderness ratio, carry a relatively small shear load in the elastic stage until the occurrence of shear buckling, but their additional capacity in the post-buckling stage prior to yielding are significantly large. They reach their ultimate shear capacity slightly after yielding. That is, their post-yield capacity is not significant. Note that the ultimate shear strength of slender plates is considerably lower than their nominal shear yield strength. In plates with intermediate slenderness ratios, material yielding and buckling occur concurrently. They carry a relatively large shear load in the elastic stage before yielding/buckling. They have also some post-buckling/post-yield reserves before failure. The ultimate shear strength of moderate plates is somewhat lower than their nominal shear yield strength. In stocky plates, yielding precedes buckling. The shear capacity in the elastic stage before yielding is thus significant. The plates have some post-yield capacity and the ultimate load is coincident with the occurrence of plastic buckling (if happens). The ultimate shear strength of stocky plates is almost equal to their nominal shear yield strength. Moreover, results of quasi-static cyclic analyses of different shear panels show that the energy absorption capability, as expected, is very sensitive to the slenderness ratio of panels and with the decrease of the slenderness ratio (increase of thickness), the absorbed energy by the panels is substantially increased. For a specific slenderness ratio, steel shear panels exhibit higher energy absorption than panels with aluminum materials (although aluminum material has higher yield strength than that of carbon steel and stainless steel materials, here). This, of course, highlights the important role of the modulus of elasticity in the energy dissipation capability of shear panels. However, the material yield strength and panel boundary conditions do not seem to have important role in the amount of energy dissipated by the panels, compared to the material modulus of elasticity.},
Keywords = {Shear panel,Plates,Cyclic Behavior,finite element method,Nonlinear analysis},
volume = {17},
Number = {2},
pages = {93-104},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9338-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9338-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Dehghani, Ehsan and Bahrani, Mohammad Kazem and Afkhami, Vahid Rez},
title = {Investigating how to model panel zone in steel frames with end plate connections},
abstract ={Abstract: In most steel frame designs the beam to column connections are assumed to be rigid or pinned but in many steel frames we have beam to column connections with semi-rigid behavior. The structures with semi-rigid connections include systems with the connections in joints which are not completely rigid, but allow, usually, some relative movements in directions of generalized displacements. Early experimental studies showed the importance of panel shear deformations for stable energy dissipation under cyclic loading. Modeling of the panel is very important for the avoidance of local failure of columns under ultimate limit state. A substantial effort has been made in recent years to characterize the behavior of semi rigid connections. Recent studies and modern codes, in especially EC3 and EC4, include methods and formulas to resistance and stiffness of panel zone. EC3 proposes a mechanical model for the semi-rigid joint in which each component is modeled by an equivalent linear spring.In these model we have some components that show with springs. These springs are assembled to form a single bilinear (elastic–plastic) rotational spring that models the connection, and is attached at the intersection between beam and column for the global analysis. Both the stiffness and strength of the springs in EC3 and EC4 depend on β factor that definition of this parameter implies an approximation of the internal forces at the joint, and therefore its use requires an iterative process at the time of performing the global analysis of the structure. So E.Bayo proposed a new component-based method (or cruciform element method) to model internal and external semi-rigid connections that revived and modified EC methods. So a cruciform element (a four-node element) is proposed to avoid β factor, and the inherent initial guessing and iterative process that it requires, and includes the finite size and deformation modes of the joint. One of main problems that structural engineer deal with is considering End Length Offset in conventional softwares. Extended end plate connection is one of beam-column semi rigid connection that we want to evaluate this behavios by using cruciform connection model and other panel zone models. In this paper three 2 dimensional frames with extended end plate connections are modeld in MATLAB using Cruciform element method and these result are compared with SAP2000 results in eight cases that in four cases panel zone are modeld and four cases are without panel zone modeling. In which of this End Length Offset considering are once just for beams and the other for beams and columns (in two case of Rigid Zone Factor : 0.5 and 1). The results show that modeling panel zones according to EC method and considering Rigid Zone Factor equal to 1 in columns and beams are best assumption to analysis of 2D frames with extend end plate connections, but if we don’t model panel zones, we must considering Rigid Zone Factor equal to 0.5 in columns and beams to give nearby actual results. Keywords: semi rigid connections, extended end plate, Rigid Zone Factor, End Length Offset},
Keywords = {semi rigid connections,extended end plate,Rigid Zone Factor,End Length Offset},
volume = {17},
Number = {2},
pages = {107-120},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-623-en.html},
eprint = {http://journals.modares.ac.ir/article-16-623-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Rezaei, Majid and Jamshidi-Zanjani, Ahm},
title = {Landfill Site Selection Using combination of fuzzy logic and multi criteria decision making Method (Case Study: Arak, Iran)},
abstract ={The rapid increase of urban population and waste production is one of the most important environmental problems in developed and developing countries. Million of tons of waste material are produced annually in the world, the correct disposal and management of which presents a main concern in the human societies. With the increase in population, and industrialization of societies accompanied by economic growth, the production of waste material has increased throughout the world. It is predicted that the population of the world will increase 2 to 3 Milliard people in the next 30 years. This means that urban waste material production will increase 3 to 4 times. Along with health and environmental adverse effects of the landfill site, emissions of carbon dioxide, the intensification of the process of global warming on a global scale also will follow. Absence appropriate supervision over management and accumulation of these outputs can engender many environmental problems, especially for people who live near the landfill to be followed. Thus, appropriate urban landfill site selection is a main issue related to the stability of cities and human environments. Geographical information systems (GIS) have appeared as useful, computer-based tools for the spatial operations like entry, storage, manipulation, analysis, and display of geographical data. Since GIS can manage a large amount of spatial data, it can serve as an ideal tool in the siting studies. In addition to the use of GIS in the landfill site selection studies, multi-criteria evaluation method to deal with the issues that decision makers and experts face with in landfill site selection is used. Combination of GIS and multi-criterion evaluation method provides a valuable tool for the solution of landfill site selection problems. In this study, fuzzy logic based on Weighted Linear Combination (WLC) were used for urban waste landfill site selection in Arak city in ARC GIS 10.1 software environment with respect to the ecological, and socio-economic parameters. In this research, reviewing the international obligations in landfill site selection and using environmental expert views on weighting the effective ecologic, and socio-economic criteria in landfill site selection it was revealed that ecologic sub-criteria, including depth of groundwater resources, distance from surface water resources, and flood potential were of great importance in urban landfill siting. Moreover, among the socio-economic sub-criteria, distance from rural and urban population centers were vital in urban landfill site selection. In the present study, after the production of the final suitability map with fuzzy logic based on WLC, the spatial desirability was divided into 5 classes. The spatial desirability for landfill sites lies in the fuzzy membership degree of between 0.3 and 0.87. Around 11033 polygons with an area of 4146.03 square kilometers were found whose spatial suitability in the fuzzy membership degree of 0.3 to 0.87. The most spatial suitability lie in the fuzzy membership degree between 0.69 to 0.87. The spatial suitability of these areas with their fuzzy membership degree is as follows: very low suitability with the fuzzy membership degree of 0.3 to 0.47, low suitability with the fuzzy membership degree of 0.47 to 0.56, moderate suitability with the fuzzy membership degree of 0.56 to 0.63, high suitability with the fuzzy membership degree of 0.63 to 0.69, and very high suitability with the fuzzy membership degree of 0.69 to 0.87. The area of the existing polygons and their number are as follows: very low suitability polygons with the area of 270.73 km2 and number of 328 polygons, low suitability polygons with the area of 683.48 and number of 1687 polygons km2, moderate suitability polygons with the area of 1187.02 km2 and number of 3006, high suitability polygons with the area of 1212.44 km2 and number of 3954 polygons, very high suitability polygons with the area of 792.36 km2 and number of 2058 polygons.},
Keywords = {site selection,Fuzzy Logic,Multi Criteria Decision Making (MCDM),Landfill,GIS},
volume = {17},
Number = {2},
pages = {120-130},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-697-en.html},
eprint = {http://journals.modares.ac.ir/article-16-697-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Rezaei, Fatemeh and Moussavi, Gholamreza and RiyahiBakhtiari, Alireza and Yamini, Yadollah},
title = {Toluene removal from waste air stream using MgO/GAC and MnO/GAC catalysts in catalytic ozonation process},
abstract ={Toluene is one of the volatile organic compounds and used extensively in industrial processes. Because of toluene effects on human health and environment, it is necessary to implement methods for toluene removal from contaminated air stream. Catalytic ozonation process (COP) is one of the emergent technologies for removal of volatile compounds from air streams. Catalytic ozonation process is an efficient, cost-effective and easy to operate for elimination of organic compounds. One of the main factors directly affecting the VOC removal efficiency and ozone destruction rate is the type of catalyst. In this study the potential of MnO/GAC and MgO/GAC catalysts was investigated for toluene elimination from air stream in the presence of ozone in a lab scale. The MnO/GAC and MgO/GAC catalysts were prepared by Sol-gel method and then characterized by BET, XRD and SEM analysis. Specific concentrations of toluene in the air were produced by using an air pump and a syringe pump. Phocheck was used to measure the concentration of toluene in gas phase. The effect of retention time (0.5-4 Sec), inlet toluene concentration (100-400 ppmv) and air temperature (25-100˚C) were investigated on catalysts efficiency in the presence of ozone. Ozone dosage (0.1 g/h) kept constant in all experiments. The efficiency of MnO/GAC and MgO/GAC were determined from the breakthrough time and removal capacity and the results were compared statistically. The BET surface area derived from N2 adsorption- desorption isotherms. From the results the BET surface area of MnO/GAC (1103 m2/g) was greater than that of MgO/GAC catalyst (1082 m2/g). XRD patterns clearly illustrate formation of MgO and MnO crystals on GAC surface. From XRD patterns the peaks at 2θ degrees of 50.3° and 73.8° were related to the MgO crystals. The peaks at 2θ degrees of 42.1°, 51.8° and 70.9° reveal the formation of Mn3O4. The crystallite phase of MgO and MnO was hexagonal and tetragonal respectively. The average size of MgO and MnO crystals was 10 and 12 nm, respectively, calculated using Debby-Scherrer equation. Results of experiments in different retention times showed that breakthrough time of MnO/GAC and MgO/GAC catalysts increased 11.3 and 13.9 times, respectively, by increasing retention time from 0.5 to 4 Sec. When inlet toluene concentration increased from 100 to 400 ppmv, the breakthrough time of MgO/GAC and MnO/GAC columns decreased 65% and 62.2%, respectively. In contrast, removal capacity of MgO/GAC and MnO/GAC was increased 39.1% and 50.4% by increasing inlet toluene concentration from 100 to 400 ppmv, respectively. The efficiency of MgO/GAC and MnO/GAC catalysts was increased 78.3% and 31.5% by increasing air temperature from 25 to 100 ˚C, respectively. These results demonstrates that increase of retention time and bed temperature could positively effect on the performance of MgO/GAC and MnO/GAC catalysts in toluene removal from waste air stream in the presence of ozone. It can be concluded that MgO/GAC and MnO/GAC catalysts had high potential in VOCs removal from air stream in the presence of ozone. The difference between the efficiency of MgO/GAC and MnO/GAC catalysts was significant (P ≤ 0.05) and MgO/GAC catalyst had higher efficiency than MnO/GAC for toluene removal from waste air in the presence of ozone.},
Keywords = {“Ozonation”,“Air Treatment”,“Catalyst”,“Manganese Oxide”,“Magnesium Oxide”},
volume = {17},
Number = {2},
pages = {131-142},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-10106-en.html},
eprint = {http://journals.modares.ac.ir/article-16-10106-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {magnification factor of drift based on demand capacity ratio of columns for various performance levels in RC frames with intermediate ductility},
abstract ={Varying the modeling of RC columns in the Updated version of in ASCE41-06 concrete provisions has been resulted in reduction of performance level of structure. This leads to a more conservative safety level in Code 2800. In this study in order to make the design in proportion with the performance level the design itself, the design criteria on code 2800 are investigated. To have a better Proportionality between structure performance level and the Code 2800 performance targets, the parameter of inelastic drift of structure is regulated. In seismic design of structures, estimating maximum inelastic lateral displacement of the structure occurring in the sever earthquake is of great importance. in most seismic design provisions, maximum inelastic displacement of the structure is estimated by amplifying the lateral displacement computed from an elastic analysis with a displacement amplification factor (Cd). Reviewing several seismic design provisions indicates that in most of them Cd is only dependent on the earthquake force resisting system. 6 RC frames with intermediate ductility and 4.5.6.8.10 and 12 stories are used for this study. For determination of real drift occurring in major earthquake (inelastic drift), nonlinear time history analysis and pushover analysis using IDARC program is performed. For linear analysis, equivalent static procedure is employed using ETABS program. In nonlinear time history analysis, 7 earthquake ground motions consistent with soil type II of Standard no. 2800 are used. These records are scaled according to Standard no. 2800 directions, Also 4 types of lateral loading patterns are used in pushover analysis, and they are triangular distribution, generalized power distribution, uniform distribution and modal distribution. For linear analysis, equivalent static procedure is employed using ETABS program. Performance level of structure elements is obtained based on the mentioned analysis. Bending forces of each of columns are calculated and compared with the strengths calculated based on the ABA. The inelastic displacements which are computed by nonlinear analysis are then divided by elastic displacements and so Cd for each story of 6 frames is determined. In most of investigating of frames, the pushover analysis and time history analysis, most of the columns are in the IO performance level and only a small percentage of them have reached the level of performance of LS. The results indicate that lower criteria limitations are needed to control the drifts and its effects on the structure level performance and response are investigated. In this research, Cd is considered as a function of R (structural behavior factor), like most researches and provisions, Finally, in order to investigate the changes in 4TH edition of code 2800, the mentioned frame is designed again based on the 4Th edition criteria and then the structure response is investigated. The results indicate that in the frames design by 4TH edition of code 2800, demand capacity ratio of bending in the upper stories of frame increases while in the lower stories There was no significant change. Furthermore the reduction in drift criteria limitations, leads to reduction in section dimensions, damage concentration in a specified story, total structure damage index and also more usage of section capacity. The latter will result in convergence of structure performance level and Code 2800 performance target.},
Keywords = {Demand capacity ratio,Magnification factor of drift,RC columns,Performance levels},
volume = {17},
Number = {2},
pages = {143-156},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5255-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5255-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Arab, Morteza and Zolghadr, Masih},
title = {Effect of Clay Content Percentage and Compaction Energy on Pier Bridge Scour in Erosive Bed and in the vicinity of Abutmnet},
abstract ={Bridge failures are fortunately rare, but every year a number of bridge collapse that has occurred somewhere in the world. In many cases these collapses could have been avoided by an adequate bridge management regime that included good inspection, assessment and maintenance procedures. One specific type of failure that from time to time causes sudden catastrophic collapse of bridges is the undermining of foundations due to bed scour. Bed scour is the transport of bed material by the flow of water and is present to some degree where the river bed is formed of granular material. Scour increases as flow rates increase and therefore the actual collapse of structures due to scour often occurs during periods of extreme flow due to flooding. Of course, this is exactly the time that direct observation of the foundations of a structure is not possible and therefore a collapse may be put down to an ‘act of God’. A good inspection regime that includes bed measurement and engineering analysis can find indications of developing scour before the situation becomes critical. If this is followed up with well-designed remedial works, undermining of the structure, even in extreme conditions, may be prevented. The formation of scour holes around bridge piers or abutment is one of the main causes of bridge foundation collapse. Local scour at bridge piers and abutment may be defined as a local lowering of the bed elevation. This lowering is mainly caused by the horseshoe vortex combined with the downflow in front of the pier and abutment, the vortex shedding at the back of the pier, abutment and the flow contraction. Bridge failure due to the effects of local scour associated with the structure of the local flow field around piers and abutment involves a considerable interest in scour prediction and scour protection measures. Two basic procedures may reduce the scour depth. The first consists in enhancing the ability of the bed material to withstand erosion. This is generally done by placing an armoring device on the bed, such as riprap. The riprap provides a physical obstacle that resists the erosive power of the flow. The second procedure consists in reducing the downflow in front of the pier and the horseshoe vortex scouring the bed material. The local scour around bridge pier and abutment in recent years has been widely studied by different authors. They proposed different methods to control the scouring depth. The most dominant concern about bridges stability is the occurrence of local scour around foundations. The local scour around bridge piers and abutments has been widely studied by different authors in recent years. They proposed different methods to control the scour depth. In order to reduce scouring around bridge piers and abutments one of the methods is the soil compaction. Compaction rise the relative density and soil resistance which mitigates scour and produce a time delay in scour hole development process. This paper focuses on the effect of clay content percentage and compaction ratio on scour reduction around bridge piers. Hence, 5%, 10%, and 15% clay was added to soil and then compacted. According to the experimental results, when 15% clay was added to non-cohesive sediment materials in saturated bed conditions with a relative density of 70%, the scour process was completely controlled after 24 hours around the bridge pier.},
Keywords = {scour,Bridge Abutment,Bridge pier,Compaction,Reduce Scour},
volume = {17},
Number = {2},
pages = {157-166},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11673-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11673-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Shariftehrani, Saleh and HosseiniLavassani, Seyed Hossei},
title = {Study of the effects of water flow and de-ice materials on asphalt concrete deterioration under freeze-thaw cycles},
abstract ={Roads and pavements are one of the most important assets in any country and considerable amount of money is paid for their rehabilitation or maintenance annually. Pavement surface is the most expensive and susceptible layer as it is in direct contact with traffic and also it experiences different environmental conditions during different seasons. Harsh weather condition and winter maintenance is another parameter that can increase the annual maintenance cost significantly. Winter snow and the resulting ice, can reduce pavement surface friction and therefore, deicing material such as deicing salt or calcium acetate are used to melt the ice and snow. Deicing material decrease the frost temperature and melt the remaining ice and snow and the resulting water flows due to the longitudinal and transverse grade over the pavement surface. The flowing water goes through longer distances in locations were the drainage system is not adequate. Although several researchers and scientists have studied the effects of deicing material on asphalt and concrete pavement deterioration, but what has not been fully studied is the simultaneous effects of deicing material and water flow on the rate of pavement deterioration under freeze-thaw cycles. Therefore, the focus of this study is to evaluate the combined effects of flowing water and deicing material on the deterioration of asphalt pavements under freeze-thaw cycles. Two types of asphalt samples were prepared and subjected to five different freeze-thaw exposure conditions. Deicing salt and calcium acetate were used as the deicing material in this study. The samples were also tested in an abrasion test apparatus and subjected to normal and frictional forces. This abrasion test apparatus was built based on the concepts used in Hamburg Wheel-Tracking Device. Marshall strength loss and weight loss of the samples were measured and used as a measure of asphalt deterioration. Results showed that the combined effects of water flow and deicers increases the deterioration of asphalt concrete samples under freeze–thaw conditions. Furthermore, deicing salt has more deteriorative effects on asphalt concrete in comparison to calcium acetate. In addition, results indicated the water flow has significant effects on asphalt concrete pavement stripping and strength loss. Water flow slows down the formation of ice during freezing cycles by not allowing or slowing the formation of ice crystals and their agglomeration. In still plain water freeze-thaw chamber, a thin ice layer was formed in zero degrees of centigrade and its depth increased during the freezing cycles but in the flowing plain water freezing condition, where the water flow was present, small ice particles started to form in areas in the chamber where the water flow was in its lowest level. Then, the ice formation gradually expanded to the area with the highest level of water flow. Besides the mentioned effects of water flow, the presence of water flow decreases the freezing temperature of water in the asphalt concrete pores and, consequently, the hydrostatic pressure inside the asphalt concrete increases significantly. Therefore, the asphalt concrete deterioration process becomes faster and more severe when water flow is present in the freeze-thaw cycles.},
Keywords = {water flow,de-icing salt,asphalt concrete pavement,Deterioration,freeze–thaw},
volume = {17},
Number = {2},
pages = {167-176},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1198-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1198-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {shahir, h},
title = {Numerical Modeling of Pile and Liquefied Soil Interaction using Non-Linear Spring Method},
abstract ={Decrease in the strength and stiffness of soil duo to liquefaction may cause large bending moments and lateral deformations in piles located in this type of soils. To reliable design of pile foundations in the liquefaction susceptible soils, it is necessary to have a accurate evaluation of the lateral pressure which will be exerted on the pile if the subsurface layers undergo liquefaction and lateral spreading in the course of earthquake. In this study, a coupled Soil-Pile-Structure Interaction (SPSI) analysis method has been used to investigate the behavior of piles in liquefiable soils. Interaction of soil-pile was simulated by using nonlinear p-y springs. The liquefaction effects were taken into account by introducing a degradation multiplier to the lateral resistance of soil. The degraded lateral resistance of liquefied soil was considered equal to 5% of its initial value for loose sand and 10% for medium sand. Fully coupled dynamic analysis of a soil column in the free-filed condition was performed in the OpenSEES (Open System for Earthquake Engineering Simulation) software. For simulation of the interaction of solid-fluid phases based on the theory of saturated porous medium, u-p formulation has been used. Liquefied soil behavior was modeled using pressure dependent multi yield material model. From the coupled analysis, the time histories of excess pore pressure ratio at the different levels are obtained. The value of excess pore pressure ratio (0.0 to 1.0) is used to interpolate the transient lateral resistance of soil from its initial value in the static condition (excess pore pressure ratio equal to 0.0) to its final degraded value in the fully liquefied condition (excess pore pressure ratio equal to 1.0). In order to verify the numerical model, results of numerical modeling have been compared with two centrifuge experiments' measurements. Both of experiments include two soil layers and the pile is extended into the lower layer. In the first experiment, the loose sand layer is above the medium dense layer and in the second experiment the medium dense sand layer is above the dense layer. After verification of the numerical model, parametric analysis was performed to study the effect of various parameters on the dynamic response of piles and applied lateral pressure from the spreading liquefied soil to pile. Investigated parameters are liquefaction layer thickness, the input excitation frequency, fixity of the pile cap, pile stiffness, maximum input acceleration and the relative density of liquefiable soil. The results of the parametric analysis show that the maximum bending moment in the case of fixed head occurs at the top of pile and in the case of free head at the depth of 1 to 3 meters. The maximum bending moment of pile is also greater in the case of fixed head pile; however, its lateral deformation is lower. Increasing of frequency of input motion and soil relative density or decreasing of liquefied soil thickness lead to decreasing of maximum bending moment and deformation of pile. Regarding the lateral pressure exerted on the pile, the results of analysis indicate that the lateral pressure is relatively constant at the depth of liquefied layer and is equal to 7 to 10 percent of the total vertical pressure at the base of liquefied layer.},
Keywords = {Liquefied soil,Pile,Interaction,Non-linear spring,coupled analysis},
volume = {17},
Number = {2},
pages = {179-191},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6110-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6110-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {SheikhAbolhasani, Ali and Vaghefi, Mohamad and Fiouz, Ali Rez},
title = {Experimental study of the effect of waterproof materials on the concrete strength and steel, polypropylene and glass fibers concrete},
abstract ={Concrete is the most widely used building materials. In the our country, Iran, the consumption amount of chemical additives materials than to the average consumption in other countries has been a significant distance and especially ready-mixed concrete industry the significant contribution of concrete production and consumption to be allocated in the country. Ready-mixed concrete industry from the most potential sections that should be pay to the valuable characteristics of the chemical additives and used to it. Therefore it is essential that developed the knowledge and technology use of chemical additives materials over the past in Iran. One of the cases that about concrete structures, especially structures that located in the vicinity of water permanent or non-permanent and chemicals materials, is important, blocked effect performance against leakage, influence, pressure or attack water containing chemical materials, addition to it is well tolerance freight its. In this context, should be made concrete that commonly “waterproof” is called. Also, to prevent cracking, high ductility, supernatural strength and energy absorption capability can be used of fiber in concrete that can be found proportional many application instances for it. Up to now specified that different types of fiber can increase strain capacity, resistance to impact, energy absorption, abrasion resistance and tensile strength of concrete. In this research, the influence of the strength of concrete and fiber concrete sealing substances has been investigated. For this purpose, concrete without fibers and fiber concrete with steel fibers, polypropylene and glass, compressive and flexural strength parameters by adding common waterproof material is studied with different percentages. In this study, by using of materials available in the Khormoj and fiber and waterproof materials, concrete parameters is evaluated of pressure and bending resistive. Carrying out tests crash sand in the province of Bushehr was used. All the stone materials in the concrete mix thoroughly washed before using in the S.S.D state. Dashtestan Cement Type 2 Compliant with ASTM C 150 is used for mixing. Thus, was carried compressive strength tests at ages 7, 28 and 90 days on the cubic test pieces and bending strength tests at ages 7, 28 and 90 days on test pieces of the cubic rectangular. Tests taken in 34 mix design and 408 samples so that in the making concrete is used of waterproof materials composition of inclusive powder sbf-wr201 (acidic neutral) and powder bc40 (acidic neutral) and liquid bc39 (alkaline) and steel, polypropylene glass fiber. In this study, a mix design based on ACI 211 recommendations for concrete without fibers by weight method was prepared. Then fibers (polypropylene, steel and glass and 2% respectively, 2%, and 1% by weight of cement) and the waterproof material (with percentages of 1, 1.5, and 2% by weight of cement) were added separately to the concrete mix design and the mix design was calculated for each compound. The tests of results show that the waterproof materials bc40 and sbf increase the strength and flexural compressive and waterproof material bc39 decreases concrete strength and flexural compressive. The most important result of this study is that to add 1 percent of waterproof materials bc40 to the fiber concrete with steel fiber has been increased 27% compressive strength compared than to control sample fiber for strength 90-day and also in the flexural strength of this combination is not seen a significant change.},
Keywords = {Water proof materials,Fiber concrete,compressive strength,Flexural strength},
volume = {17},
Number = {2},
pages = {193-201},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5809-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5809-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {nasiri, FARZIN and Alavinia, Morteza and Asadi, Hossei},
title = {Effects of variabl rainfall intensity events on interrill erosion},
abstract ={Soil erosion, as a complicated natural phenomenon, is a global challenge threatening soil and water resources. Therefore, accurate understanding of soil erosion and sediment transport processes and their interactions is necessary for prediction of soil erosion.To distinguish between the dominant processes involved in soil loss, soil erosion has been classified into rill and interrill erosion. Rainfall-induced detachment and transport of sediment have a fundamental contribution to interrill and sheet erosion. Instead of the observation of natural rain showers, simulation of rainfall is widely used for better understanding of processes involved in soil erosion and their interactions. Rainfall intensity is variable during a natural rain showers, such that peak rainfall intensity in an event can exceed the mean event intensity by an order of magnitude. Variations of rainfall intensity during a rainfall event is called ‘event profile’. However, the available information is inadequate to understand its effects on runoff and soil loss processes. Thus, this study was aimed to quantify the effect of event profile on runoff and soil loss in rainfall-induced erosion. The experiments were based on the use of simulated rainfall on disturbed soils in a small laboratory detachment tray. Since kinetic energy controls runoff and soil loss processes, the effects on the soil surface of rainfall events with the same average intensity may be different. Hence to study only the effects of event profile, we used four simulated rainfall events, each with a different profile but all delivering the same total kinetic energy to the soil surface. The study was conducted in the rainfall simulation laboratory, Department of Hydraulic, Faculty of Civil and Environmental Engineering, Tarbiat ModaresUniversity, Iran. For this study, four events with different temporal profiles of rainfall intensity, each with the same kinetic energy, were chosen; (a) constant intensity, (b) increasing intensity, (c) decreasing intensity and (d) increasing - decreasing intensity. The soil samples used in the experiments were a sandy soil (soil A) and a sandy loam soil (soil B). Disturbed soil samples were collected, air dried, crushed to pass a 4.75-mm sieve, and thoroughly mixed. For each experiment soil was packed into a drainable detachment tray to a specific bulk density. The test area of this tray was 15cmwide by 30cmlong and 15cmdeep.Eliminating the effects of soil moisture on results, soil was saturated from the bottom using drainage outlet tube connected to a water reservoir 24hr before each experiment. The tray was setup at a slope of 0.5% and exposed to simulated rainfall events. For each simulation, runoff and sediment were sampled at regular intervals. Our results showed that while the peak runoff was affected by event profile for the two soil types, there was no significant difference in total runoff among rainfall events examined for both soil types. However, our experiments showed that soil type significantly affected the soil loss. In addition our results showed that models that derive interrill soil erosion directly from rainfall intensity can, therefore, be expected to perform poorly in predicting soil erosion from varying intensity rainfall events. It may imply that various and complicated mechanisms might be activated for runoff and erosion under natural rainfall conditions. Our results may indicate that negligence of event profile may lead to inaccurate understanding of mechanisms involved in runoff and soil erosion.},
Keywords = {Event Profile,runoff,Sediment,Rainfall Simulation,Interrill Erosion},
volume = {17},
Number = {2},
pages = {203-213},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12113-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12113-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Mousavi, Sayed-Farh},
title = {Analysis of time series in hydrological processes using chaos theory (Case study: Monthly rainfall of Urmia Lake)},
abstract ={Scientific method for correct recognition and understanding of the hydrologic phenomena is investigation of their simple models. Generally, a model is a simple representation of a complex system. In mathematical models, behavior of the system is described by a series of mathematical equations, along with logical relationships between variables and parameters. Despite the various proposed mathematical models for modeling of the hydrologic phenomena, there is not a unique approach in this respect. This might be due to spatial and temporal variability of hydrologic phenomena and also lack of mathematical tools for extraction of proper structure for these phenomena. These variations are the result of dependability of the phenomena on different components. This problem has caused the past researches on hydrologic modeling to view the situation as random and probabilistic. The performance of most natural phenomena, including hydrologic problems, in short time scales, to be viewed as completely random and without any trend. But, with a change in time scale, and using sophisticated models, a type of interval and order will be observed. Nowadays, researchers believe that hydrologic phenomena, which have dynamic and nonlinear nature, could be better analyzed by nonlinear and deterministic chaotic models. Hydrologic components in lakes have non-linear and dynamic nature. But, since the changes that these components create in the lakes don’t happen suddenly, it is possible to study and predict some of these elements in the hydrologic cycle. Nowadays, with the evolution of computer models, it is believed that analysis, modeling and control of complex natural phenomena, including hydrologic processes, could be better performed with chaotic models than probabilistic models. Studying the hydrologic components in analysis of the water resources systems, such as lakes, is very important in their quantitative and qualitative operation and management. Due to the importance of precipitation in variations of water level in Urmia Lake, located in north-western Iran, the chaos theory could be a powerful approach to analyze and model the complex behavior of such phenomena. Investigation of chaotic or random behavior of rainfall time series in the lake, for the choice of the best suited rainfall simulation approach, is an important and controversial issue that has been dealt with in this research. First, using the correlation dimension method (CDM), the monthly rainfall time series of Urmia Lake was analyzed over a period of 40 years (1967-2007). After calculating the delay time using average mutual information (AMI) and also calculation of the embedding dimension using false nearest neighbor (FNN) algorithm, the phase space was reconstructed and then the correlation dimension was determined. Then, by using Lyapunof exponent and Fourier power spectrum, the existence of chaos was investigated. Results revealed that presence of chaos in the rainfall time series of Urmia Lake is evident with the non-integer CDM of 2.56, positive value of Lyapunof exponent (maximum of about 2.5) and broad band Fourier power spectrum. Consequently, the system behavior is regular; in other words, the system is not considered random. In such a system, chaos theory has the ability to extract short-term time series from long-term records. In addition, the existence of low-dimensional chaos implies the possibility of accurate short-term predictions of precipitation.},
Keywords = {Correlation dimension,Urmia Lake,Fourier power spectrum,Lyapunof exponent},
volume = {17},
Number = {2},
pages = {213-223},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11598-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11598-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Keshtegar, Behrooz},
title = {Parametric Study of Pitting Corroded Steel Bars for Reinforcement Concrete Beams using Statistical Analysis},
abstract ={Corrosion of steel reinforcement has a complex process which leaded the reduction of crass section bars and degradation of concrete structure. the corroded reinforcement bars were the most important issue of the concrete permanence in the marine structures. The important effects of corrosion are in the damages made by corroded concrete structure which include all kinds of structural and non-structural damages. The first one is more important because of the reduction of the safety factor of the structure against the applied external loads. These failures include the reduction of cross-section bars and the changes in the steel mechanical behavior. Corrosion includes two processes: (1) corrosion initiation and corrosion propagation. The initiation time is when the corrosive ions receive on the surface bars and lead to activation of the steel. (2) The propagation time is when the structure loses its capability subject to the loss of the cross-sectional area of reinforcing steel bars, reduction of bond and crack initiation and propagation. The predicative models of life-service of a reinforced concrete structures should be included the two processes of corrosion. Because for new structures, the initiation time of corrosion and insurance from the long-time of corrosion initiation time, and for the existing structures, controlling the corrosion propagation is more important. In this paper, statistical characteristics of the chloride diffusion coefficient, corrosion initiation time and corrosion rate including the best probability distribution function and its parameters are investigated based on Mont Carlo simulation of pitting corrosion data. The distribution function parameters of the corrosion variables i.e. the chloride diffusion coefficient, corrosion initiation time and corrosion rate were calculated using the Maximum likelihood method based on mathematical pitting corroded model that corrosion initiation and corrosion propagation processes are considered in this model. the probability density functions such as: Gamma, Gumbel, Lognormal, Normal, and Weibull were used in the statistical analyses of corroded pitting parameters. The best probability distribution function was selected using chi-square statistic. the Lognormal distribution function was obtained the best probability function for the threshold chloride concentration, the corrosion initiation time and the corrosion rate. The corrosion initiation time depend on four basic random variables such as: the concrete compressive resistance, the concrete cover, the threshold chloride concentration and the surface chloride concentration. Thus, their statistical effects of these random variables on corrosion initiation time are parametrically investigated using 10000 Mont Carlo simulations. It is obvious that increasing the concrete resistance leads to increasing the corrosion initiation time and standard deviation of the density function. The concrete physical and mechanical characteristics are effective variables on the corrosion initiation time but the threshold chloride concentration and the surface chloride concentration are insensitive variables on the mean of corrosion time but lead to significant changes in standard deviation of the corrosion time. Finally, Various diameters bars such as: 8, 12, 16 bars and 20 were investigated in time-depended area of the corroded steel of concrete beams. Results illustrated that and the cover depth is important variable in corroded crass section of bars. Also, increasing the bar diameter and decreasing the corrosion time period were leaded to reduce the rate of the crass section bars.},
Keywords = {Probabilistic analysis,Mont Carlo simulation,reinforced concrete beams,pitting corrosion},
volume = {17},
Number = {2},
pages = {235-246},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6968-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6968-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Younesi, Habibollah and Mahdad, F. and Bahramifar, Nader and Hadavifar, Mojtab},
title = {Optimization of Compost Leachate Treatment Using Advanced Oxidation Process )AOP (H2O2/UV},
abstract ={Composting is certainly one of the most natural types of recycling process. One of the problems during this process is the management of leachate that adversely affects human and ecological health in the area. Leachate is a complex organic compound which is difficult to be degraded biologically by conventional methods. Advanced oxidation processes (AOPs) have been widely studied for the degradation of diverse types of industrial wastewaters. The purpose of the study was aimed to evaluate the efficiency of hydrogen peroxide with ultraviolet light (H2O2/UV) for the treatment of high chemical oxygen demand (COD) strength compost leachate, color and turbidity using response surface methodology (RSM) under central composite design (CCD). The various operation conditions such as initial pH, dose of hydrogen peroxide, and UV-contact time was examined in order to optimize the maximum COD and color removal and turbidity of the compost leachate. The total number of 20 experimental runs was set. Optimal condition obtained for H2O2/UV process were initial pH 7.5, dose of hydrogen proxide 2.3 mL/L, and UV-contact time 95 min. In these conditions, the removal of COD and color and turbidity for H2O2/UV process was 12.32%, 20.83%, and 8.68 NTU, respectively. The results indicated that the H2O2/UV process has been successful in reducing turbidity but in COD removal efficiency is not well. Composting is certainly one of the most natural types of recycling process. One of the problems during this process is the management of leachate that adversely affects human and ecological health in the area. Leachate is a complex organic compound which is difficult to be degraded biologically by conventional methods. Advanced oxidation processes (AOPs) have been widely studied for the degradation of diverse types of industrial wastewaters. The purpose of the study was aimed to evaluate the efficiency of hydrogen peroxide with ultraviolet light (H2O2/UV) for the treatment of high chemical oxygen demand (COD) strength compost leachate, color and turbidity using response surface methodology (RSM) under central composite design (CCD). The various operation conditions such as initial pH, dose of hydrogen peroxide, and UV-contact time was examined in order to optimize the maximum COD and color removal and turbidity of the compost leachate. The total number of 20 experimental runs was set. Optimal condition obtained for H2O2/UV process were initial pH 7.5, dose of hydrogen proxide 2.3 mL/L, and UV-contact time 95 min. In these conditions, the removal of COD and color and turbidity for H2O2/UV process was 12.32%, 20.83%, and 8.68 NTU, respectively. The results indicated that the H2O2/UV process has been successful in reducing turbidity but in COD removal efficiency is not well. The results indicated that the H2O2/UV process has been successful in reducing turbidity but in COD removal efficiency is not well.},
Keywords = {H2O2/UV,CompostLeachate,Wastewater treatment,AOPs,H2O2/UV},
volume = {17},
Number = {2},
pages = {247-258},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-305-en.html},
eprint = {http://journals.modares.ac.ir/article-16-305-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Seismic capacity and possibility of collapse of tall steel buildings with outrigger system using failure curves and damage profiles]},
abstract ={forms of the outrigger or belt truss structure have high performance in reducing the response of tall structures against side loads. However outriggers system are not considered as a seismic system in design codes. In this paper seismic behavior of tall buildings with outriggers will be checked and the effect of adding outrigger on the seismic behavior of steel tall structures in term of capacity of seismic intensity corresponding to the level of performance of collapse, Distribution of seismic requirements in high of structures demand curves corresponding to the general instability of structures and Fragility curves will be studied. Therefore, in the first three buildings of 20, 25 and 30 floors in three dimensions are designed so that the effects of outriggers not considered in the initial design and in terms of members resistance and the relative displacement (drift) have passed some regulations. To do this, the three structures is designed using 3D model So that the effects of outrigger are not considered in the initial design and in terms of resistance members as well as the relative displacement of stories have passed limits of design code. and then one of main frame of structure is analyzed using “Opensees” software and moment frame structural system and CBF with regard to inelastic behavior in both the presence and absence of outrigger checked by IDA analysis. The results show Keywords: Tall Building, Outrigger and Belt Truss, Seismic behavior, Incrimental Daynamic Analysis. forms of the outrigger or belt truss structure have high performance in reducing the response of tall structures against side loads. However outriggers system are not considered as a seismic system in design codes. In this paper seismic behavior of tall buildings with outriggers will be checked and the effect of adding outrigger on the seismic behavior of steel tall structures in term of capacity of seismic intensity corresponding to the level of performance of collapse, Distribution of seismic requirements in high of structures demand curves corresponding to the general instability of structures and Fragility curves will be studied. Therefore, in the first three buildings of 20, 25 and 30 floors in three dimensions are designed so that the effects of outriggers not considered in the initial design and in terms of members resistance and the relative displacement (drift) have passed some regulations. To do this, the three structures is designed using 3D model So that the effects of outrigger are not considered in the initial design and in terms of resistance members as well as the relative displacement of stories have passed limits of design code. and then one of main frame of structure is analyzed using “Opensees” software and moment frame structural system and CBF with regard to inelastic behavior in both the presence and absence of outrigger checked by IDA analysis. The results show Keywords: Tall Building, Outrigger and Belt Truss, Seismic behavior, Incrimental Daynamic Analysis. To do this, the three structures is designed using 3D model So that the effects of outrigger are not considered in the initial design and in terms of resistance members as well as the relative displacement of stories have passed limits of design code. and then one of main frame of structure is analyzed using “Opensees” software and moment frame structural system and CBF with regard to inelastic behavior in both the presence and absence of outrigger checked by IDA analysis. The results show Keywords: Tall Building, Outrigger and Belt Truss, Seismic behavior, Incrimental Daynamic Analysis.},
Keywords = {Tall Building,Outrigger and Belt Truss,Seismic behavior,Incrimental Daynamic Analysis},
volume = {17},
Number = {4},
pages = {1-13},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9184-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9184-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {amirzehni, hasan and shafei, erf},
title = {An Investigation of the Effect CFRP Post Tensioned Cables on Seismic Behavior of Steel Braced Frames with Controlled Rocking System},
abstract ={Conventional lateral force resisting systems, dissipate seismic energy through plastic deformation in primary structural members that results in significant damage in buildings. In most cases, repair of these induced damages are impossible from the structural viewpoint, or have not economic justification. Recent research works are to localize the induced damage to specific elements (as fuse, dampers and etc.) without plasticization of primary load-carrying elements that ensure the stability of structure. In steel structures, the self-centering rocking braced system is an innovative type of seismic lateral force resisting systems that is developed with aim to minimize structural damages, residual drifts and enable repair or replace of damaged elements with minor expense after experiencing earthquakes. Steel braced frame with controlled rocking system consists of three primary components: (1) steel braced frame with rigid joints and no connections to base foundation at the column bases that is free to rock cyclically during excitation; (2) post tensioning cables which are connected to the frame top and foundation base in order to provide retreat back or self-centering capability of the system. Expressed mechanism plays an important role in restoration of quake-imposed displacement into its initial position; and (3) the replaceable energy dissipating elements that act as structural fuses to absorb seismic energy through undergoing of inelastic deformations and provide the required ductility of the system prior to instability or collapse. In this type of lateral force resisting systems, the post tensioned cables and the members of the braced frame are design to remain elastic during excitation and provide high stiffness, strength and global stability of the structure with minor local deformations. In this design concept, post tensioned strands are the key members known in providing self-centering capability of the system and occurrence of any plastic deformation in these elements endangers overall stability of system. Probable exceedance of seismic force may result in yield of post-tensioned cables and consequent elimination of restoring functionality of self-centering mechanism. In current research work, the steel material is replaced by carbon fiber reinforced plastic (CFRP) fabric in post tensioning strands, and the consequent effects of proposed substitution is investigated on the behavior of braced frame and linked structural components. The research was conducted on two steel braced frames with controlled rocking system equipped with steel and CFRP cables and the models are analyzed using nonlinear dynamic time history analysis (NLTHA) procedure. The frames are subjected to JMA-Kobe ground motion record, that is scaled to 69%, 100% and 120% intensity groups which corresponds to unit, 1.45 and 1.74 times of maximum considered earthquake (MCE) ground motion level. Extracted results show that using CFRP post tensioned cable instead of steel cables, can protect the system against instability even under 100% Kobe ground motion record scale and leads to a more reliable type of controlled rocking systems. This study also revealed that remaining the CFRP cable on elastic region not only controls the frame lateral displacement, also prevents early failure in fuses under severe earthquakes and ensures the seismic energy dissipating capability of the structure.},
Keywords = {Self-Centering System,Post-Tensioned Cable,Energy Dissipating Fuse,CFRP,Controlled Rocking System},
volume = {17},
Number = {4},
pages = {15-25},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11138-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11138-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Taghipour, Shabnam and Ayati, Bita and Razaei, Mi},
title = {Study of the SBAR performance in COD removal of Petroleum and MTBE},
abstract ={The petroleum refineries, water are used for different purposes, such as extraction of contaminants. Some of these pollutants such as petroleum and Methyl Tertiary Butyl ether (MTBE) can be noted that have less biodegradability than other organic compounds. Discharge of these pollutants into water, and the presence of them in drinking water make huge environmental concerns. A sequencing airlift reactor (SBR) along with an internal riser is called sequencing batch airlift reactor (SBAR); it has a similar structure to SBR and purifies wastewater with a certain temporal cycle in a single reactor. The SBAR system, which is used along with granules to treat wastewater, is known as granule sequencing batch airlift reactor (GSBAR). Using this system for biodegrading requires a high concentration of biomass (aerobic granules. In recent years, several studies have been conducted on the use of aerobic biogranules. Mousavi et al., examined the removal of phenol with an initial concentration of 1000 mg/L from saline wastewater using GSBAR with aerobic granules 2 mm in size. The results indicated that 99% of phenol was removed. Bao et al., studied the effect of temperature on the formation of aerobic granules and on the removal of nutrients by SBAR system. The granules had an average diameter of 3–4 mm, density of 1.036 g/mL, sludge volume index of 37 mL/g, and sedimentation rate of 18.6–65.1 cm/min. The input load rate of COD, NH4–N, and PO4–P was 1.2–2.4, 0.122, and 0.012–0.024 kg/m3/day, respectively and the removal efficiency at low temperatures was 90.6–95.4, 72.8–82.1, and 95.8–97.9%, respectively. Taheri et al., examined the formation of aerobic granules in SBR for treating saline wastewater. In this study, the granules were 3–7 mm in size, had a fall speed of 0.9–1.35 cm/s, and density of 32-60 g/L. Using aerobic granules with a diameter of 1–2 mm to biologically restore 2, 4-di-chlorophenol with an initial concentration of 4.8 mg/L, Wang et al., achieved the removal efficiency of 95% and 94% for COD and di-chlorophenol, respectively. Siroos Rezaei et al. reported that COD removal efficiency of synthetic wastewater was 95% with the glucose carbon source in six 4-h cycles with a loading rate of 1500 mg/L in SBAR system using aerobic granules. The new granules had different diameters in the range of 0.5–5 mm, high sedimentation ability, and SVI of 100 mL/g. Ghaderi et al., investigated the performance of the biofilm reactor and SBR in removing formaldehyde from wastewater. The results revealed that removal efficiency of CODs less than 200 mg/L was 100% and removal efficiency of CODs between 200–450 mg/L was 90% after 48 h. The aim of this study was evaluating the ability of SBAR system in quick produce of granules and achieving high removal of petroleum and MTBE in a short time. For this purpose, 2 similar SBAR systems with Circular cross-section were used. Outer Cylinder's diameter and length was respectively 8cm and 110 and the internal riser's diameter and length was respectively 4 cm and 90 cm. In the first system (R1) petroleum was treated in 6 hours and in the second system (R2) MTBE wastewater was treated in 4 hours. In COD equivalent to 600 mg/L, the removal efficiency of R1 and R2 were equal to 81.1 and 84.2%. These values were respectively 82.8 and 90% in COD equivalent 500 mg/L. Consider to granules changes, optimal COD was respectively equivalent to 600 and 500 mg/L in R1 and R2. By reducing retention time to 5 and 3 hours in R1 and R2, removal efficiency of pollutants in optimal COD of each system was respectively 77.8 and 90 %. The first granules were observed in the seventh day of operating system. During this period, the size of the granules increased to 1.3 and 0.6 mm in R1 and R2. Density and velocity of the granules were in the range of 0.0252-1.1998 gr/mL and 3.02-3.32 cm/s in R1 and 0.05-0.06502 gr/mL and 0.4-0.9 cm/s in R2. SVI was in the range of 42-65 mL/g, pH and DO was in the range of 6.8-7.2 and 2-6 mg/L and ORP was always above 100 mV.},
Keywords = {COD,COD,Arobic granule,petroleum pollutant,MTBE},
volume = {17},
Number = {4},
pages = {17-27},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7139-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7139-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {dalvand, ahm},
title = {Experimental study on impact behaviour of high performance concrete with statistical approach},
abstract ={High-performance concrete (HPC) exceeds the properties and constructability of normal concrete. Normal and special materials are used to make these specially designed concretes that must meet a combination of performance requirements. Special mixing, placing, and curing practices may be needed to produce and handle high-performance concrete. Extensive performance tests are usually required to demonstrate compliance with specific project needs (ASCE 1993, Russell 1999, and Bickley and Mitchell 2001). High-performance concretes are made with carefully selected high-quality ingredients and optimized mixture designs; these are batched, mixed, placed, compacted and cured to the highest industry standards. Typically, such concretes will have a low water-cementing materials ratio of 0.20 to 0.45. Plasticizers are usually used to make these concretes fluid and workable. High-performance concrete has been primarily used in tunnels, bridges, and tall buildings for its strength, durability, and high modulus of elasticity. High Performance concrete (HPC) are a class of fiber cement composites with fine aggregates that exhibit tensile strain hardening response under uni-axial loading. These materials are characterized by pseudo-ductile tensile strain hardening behavior and multiple cracking prior to failure. This figure emphasizes the transition from brittle concrete to quasi-brittle FRC (strain softening behavior after first cracking) to ductile HPFRCC with strain hardening behavior after first cracking. In recent years, a new class of HPFRCC has emerged as ECC. Engineered Cementitious Composite (ECC) which was developed at University of Michigan had a typical moderate tensile strength of 4-6 MPa and ductility of 3-5%.Since there is not enough available information to give mechanical characteristics and also to calculate the mean, standard deviation and coefficient of variation, some statistical evaluations are necessary to obtain accurate results of the effect of inclusion of PP fiber on absorbed energy and impact resistance of concrete. Concrete is a heterogeneous material, and that is why results obtained from several tests are often significantly scattered. There is a few quantitative statistical data about the effect of PP fiber on compressive, flexural strength of HPC at the other research work; therefore it shows a necessity to study the effects of PP fiber on mentioned parameters.Gotten data were statistically analyzed. 240 concrete specimens were prepared in three series with different mix designs, containing 0.5, 0.75 and 1 percent of PP fibers. Twenty 100×100×100mm cubic specimens, twenty 320×80×60mm beam specimens andforty150×64mm discs were cast from each mixture. Cubic specimens were used to determine the compressive strength, beam specimens were tested to obtain flexural strength and cylindrical cutting specimens (discs) were subjected to the drop-weight test following the ACI committee 544 to determine impact strength of mixed concretes. Statistical analysis done based on these experimental tests showed that in comparison with data of impact strength, data of mechanical properties have less dispersion. Also while increasing percentage of fibers, dispersion in data increases. According to results of compressive strength test on cubic specimens, adding fibers to specimens increased the coefficient of variations of compressive strength. The coefficient of variations of compressive strength for HPFRCC was increase from 4.96 % to 8.42 %. Also Statistical data for flexural strength are almost normally distributed. Mean flexural strength in HP-1 group (1% fiber) was 6.24 MPa, which is 29 % and21 % more than HP-0.5 group (0.5 % fiber) andHP-0.75 group(0.75 % fiber), respectively. HP-1 group's coefficient of variation is 9.88 % which is 11 % and 8 % more than the same parameter in HP-0.5 and HP-0.75 groups, respectively.},
Keywords = {High-performance concrete,Statistical data,Impact behavior,Flexural strength},
volume = {17},
Number = {4},
pages = {39-49},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7736-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7736-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Dehghani, Ehsan and AllamehNajafi, S. Mahdi and AllamehNajafi, S. Ali},
title = {Behavior assessment of common shear walls in iran with steel boundary element},
abstract ={Abstract: Composite construction in steel and concrete offers significant advantages for use as the primary lateral resistance systems in building structures subjected to seismic loading. While composite construction has been common for over half a century through the use of composite beam and joist floor systems, over the past decade a substantial amount of research has been conducted worldwide on a wide range of composite lateral resistance systems. These systems include unbraced moment frames consisting of steel girders with concrete-filled steel tube (CFT) or steel reinforced concrete (i.e., encased steel sections, or SRC) beam-columns; braced frames having concrete-filled steel tube columns; and a variety of composite and hybrid wall systems. Structural walls are widely used in building structures as the major structural members to provide substantial lateral strength, stiffness, and the inelastic deformation capacity needed to withstand earthquake ground motions. In recent years, steel reinforced concrete (SRC) walls have gained popularity for use in high-rise buildings in regions of high seismicity. SRC walls have additional structural steel embedded in the boundary elements of the reinforced concrete (RC) walls. Walls with additional shapes referred as composite steel-concrete shear walls, contain one or more encased steel shapes, usually located at the ends of the wall. Composite shear walls with steel boundary element are known as the structural members able to withstand high in-plane lateral forces at low displacement levels. Reinforced concrete shear walls with steel boundary element being performed in Iran are joined to the foundation, in boundary element section, usually through bolts and base plates. Most reliable codes of the world have nothing to say about the behavior of this type of shear walls, and no experimental studies or analyses have been conducted on the behavior of this type of shear walls. In the past decade, great effort has been devoted to the study of seismic behavior of SRC walls, for Design provisions for SRC walls have also been included in some leading design codes and specifications, for example, AISC 341-10 , Eurocode 8, and JGJ 3-2010 Exposed baseplates together with anchor bolts are the customary method of connection of steel structures to the concrete footings . In this paper, the influence of cross section of base plate’s joint bolts to the foundation and the wall’s longitudinal bars embedding within the area of boundary element in the foundation, on the behavior of this type of shear walls have been investigated. The finite element software is first calibrated and the accuracy of its results is validated through modeling the experimental samples. In this research, the concrete’s nonlinear finite element analysis method and concrete damage plasticity model have been used for the concrete’s behavior modeling. The results show that increasing in the level of bolt’s cross section and also the embedding of longitudinal bars of boundary element in the foundation cause an improvement of the capacity of these walls. However, these walls’ resistance against the normal axial loads is considered to be less than reinforced concrete shear wall. Keywords: Reinforced concrete shear wall, Steel boundary element, Concrete damage plasticity model, Finite element model.},
Keywords = {Reinforced concrete shear wall,Steel boundary element,Concrete damage plasticity model,Finite element model},
volume = {17},
Number = {4},
pages = {51-62},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7253-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7253-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Investigation behavior of bearing 3D Panel wall developed by lateral load in independent and system states},
abstract ={The three dimensional panels are one of the modern building systems which can be placed in the category of industrial buildings. It has always been tried to conduct many studies for identifying the behavior and upgrading the capacity of panels due to their earthquake resistance and high speed performance. In this regard, in this research a comparative study of structural components behavior of the upgraded three-dimensional panels under lateral load in independent and system mode, is investigated. At the same time it is tried to study the effect of strengthening the three dimensional panels and system mode (independent wall, L-shaped and BOX-shaped walls) on the three-dimensional panels. In order to verify, the results of panel were compared with dimensions of 120 × 120 with laboratory results of Kabir and Jahanpour and the results indicate the validity of the model. In the following, twenty-four models with dimensions close to reality (360 × 360〖cm〗^2), are built with Abaqus software. Overall, six independent wall model, L-shaped, roofed L-shaped, BOX-shaped walls with symmetric loading, BOX -shaped wall with asymmetrical loading and roofed BOX-shaped wall were built. Then the models are strengthened without strengthened reinforcement and with strengthened reinforcements ( 10) with an angle of 30, 45 and 60 degrees. The applied lateral loading, is exerted by changing the location on the end wall. After applying the loading, the pushover curve is plotted from which the maximum lateral load bearing capacity, the absorbed energy are obtained. It is warth mentioning for drawing the push over curve the target displacement is determind by ATC 24 guideline. And also for drawing the histories careature ATC40 guidline is used. The evaluation of results showed that the lateral load bearing capacity of L-shaped wall without strengthened reinforcement is not more than independent wall, but also it will be less. But by adding roof to the structure, the load bearing capacity will be increased due to reducing twisting effect. If strengthening the wall occurs, in roofed and without roofed modes, the capacity will be increased about 50 and 100 %. In BOX-shaped wall, in symmetric and asymmetric loading, the load bearing capacity will be increased about 200 and 50 % respectively. Now, if strengthened, the load bearing capacity in symmetric and asymmetric loading will be increased 3.5 and 2 times respectively. The effective angle of placement of strengthened reinforcement in the independent wall is 45 and 60 degrees. But in BOX-shaped and L-shaped walls, the use of strengthened reinforcement 45 degrees is recommended. In the L-shaped wall alone (not the entire system), the capacity will be increased 21 % and by adding roof, the load bearing capacity will be approximately two times. This mode in the BOX-shaped wall with symmetrical loading will be 63 %. By generally comparing the histories cerratures it is resulted that the L-shaped wall wich has the torsion originated from loading, has a lower energy dissipation in comparison with the models. And also if the exsting story loads to the integrated performance of the walls, it can.},
Keywords = {Three-dimensional Panels,Independent and System mode,Upgrading the Load Bearing Capacity,Strengthening the Panel},
volume = {17},
Number = {4},
pages = {63-75},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1051-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1051-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Roohi, Pejman and Fatehifar, Esmaeil and Alizadeh, Rez},
title = {Modeling and optimization of fast degradation of contaminated soil with 2-methylpropane-2-thiol by modified Fenton process},
abstract ={The pollution of soil with 2-methylpropane-2-thiol as an odorant hydrocarbon is an environmental problem. It also causes secondary impacts such as social dissatisfaction and economic problems due to tourist revenue reduction. 2-methylpropane-2-thiol is a hazardous material and remediation of soil polluted by this material with a fast method is important to study. In this study, modified Fenton treatment is investigated for oxidation of 2-methylpropane-2-thiol. Central Composite Design (CCD) based on Response Surface Methodology (RSM) was used to obtain appropriate effects of the main factors (initial H2O2 concentration, FeSO4 to soil ratio and stirring time interval percentage) and their interactions on the removal efficiency. Treatments were set up to monitor 2-methylpropane-2-thiol removal efficiency for initial contaminant concentration of 64690 part per million by weight. Samples were analyzed by gas chromatograph equipped with FID and TCD detector and HP-Plot Q column. Design of experiment in the three-factor with five-level matrix include 20 experiment. Randomization technique is used to guard against unknown and uncontrolled factors as lurking nuisance factors. Moreover, blocking technique is used for investigation of probable effect of initial soil temperature on results. Analysis of variance and Pareto analysis show that all main factor are effective. Also, stirring time interval percentage was the most influential factors on 2-methylpropane-2-thiol removal efficiency. Results of the experiments shows that at low concentration levels removal efficiency increases with hydrogen peroxide concentration up to the certain level. For higher concentration of hydrogen peroxide concentration, the removal efficiencies decreased which could be due to scavenging. Also, increasing in FeSO4:Soil ratio increases removal efficiency up to the certain level because Fe2+ is an alternative to enable more extensive and greater contaminant oxidation; however a greater ratio (greater than 0.0040) causes decrease in the removal efficiency. This phenomena could be due to side reactions which affect reactive radicals such as OH• radicals. Furthermore, investigation of the results demonstrates that 2-methylpropane-2-thiol removal efficiency rises with increasing stirring time interval percentage. This phenomena could be due to uniform distribution of oxidation agent and Fe2+ and better desorption of contaminant from soil to liquid phase. Moreover, based on analysis of variance, the interaction between hydrogen peroxide and FeSO4: Soil ratio was significant with positive effect on the removal efficiency. This interaction could be the result of reaction between H2O2 and Fe2+. By considering main and interaction effects, with the raising H2O2 and Fe2+ concentration up to a certain level, the removal efficiency increase and with further concentration increasing the removal efficiency will be dropped. Analysis of variance indicate that initial soil temperature (21 and 25 0C) were not effective factors during the time interval of the experiments which could be due to the exothermic reaction between hydrogen peroxide, FeSO4 and contaminant. P-value of lack-of-fit (0.064) indicates that suggested model adequately fits the data with good correlation coefficient (R2=95.12%). Optimum condition suggested for maximum 2-methylpropane-2-thiol removal efficiency (94.412%) shows that concentration of H2O2 and Fe2+ ion must be at the certain level and maximum stirring time for remediation in the studied intervals. CCD model predict 94.084% for the removal efficiency at optimum condition which is good agreement with the predicted value.},
Keywords = {"2-methylpropane-2-thiol","Quadratic mathematical model","Analysis of variance","remediation"},
volume = {17},
Number = {4},
pages = {77-88},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-3531-en.html},
eprint = {http://journals.modares.ac.ir/article-16-3531-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Development of a Vertical Design Spectrum for Iranian Plateau Using V/H Spectral Ratio},
abstract ={In last two decades, some earthquakes like Kobe (1995), Chi-chi (1999) and Bam (2003) have shown the importance of vertical component of ground motion in inflicting damage on a variety of structural systems. Moreover, it has been shown that the effects of vertical component of earthquake in structural responses are more pronounced in the near fault regions. Therefore, It seems that, both horizontal and vertical design spectra are required in structural design procedure to reduce the vulnerability of structural systems to seismic loads. However, some of the existing design codes or guidelines are providing the designers only with the horizontal spectrum. In some others, the vertical spectrum is defined using a unified ratio of 2/3 with respect to the horizontal one. A new trend in design codes approaches is to introduce vertical design spectrum for the ground motion. Typically, there are two approaches in obtaining the vertical component of response spectrum using Ground Motion Prediction Equations (GMPEs). The differences between these approaches are based on the method of using GMPEs in development of vertical spectrum. The first approach is a direct application of GMPEs for vertical component of earthquake and in the second one; the attenuation model is in the form of vertical to horizontal spectral ratio function (V/H). The attenuation model in this case is used to scale the horizontal spectrum to the vertical one. While V/H ratio usually scales down the horizontal spectrum, it may scale up the spectrum in near distances particularly for the short period range of the response spectrum. GMPEs have a key role in seismic hazard evaluation for site-specific spectra. To propose a GMPE for any specific region the magnitude, source-to-site distance and peak ground characteristics of earthquakes in that region are required. In addition, some other parameters such as site class, faulting mechanism and so on might be considered necessary in development of GMPEs for a particular region. Although, various GMPEs have been developed for horizontal component of earthquake, there are no reliable GMPEs for vertical component of earthquake in Iranian plateau. In this study, after selecting the required GMPEs (GMPEs for horizontal and vertical component as well as GMPE for vertical to horizontal spectral ratio), the integrity of the results for development of vertical spectrum is evaluated. The sensitivity analyses for the V/H model show the relative independancy of this ratio to the magnitude and faulting mechanism of earthquakes (as well as site classes). Therefore, the source-to-site distance parameter is chosen as the sole contributor in defining the V/H ratio. Later, a simplified model for V/H ratio in terms of distance (source to site) is proposed in this study. Seismic hazard analysis for vertical component of earthquake is performed using V/H at a desired site and compared with the results of uniform hazard spectrum (UHS) analysis for the same component of earthquake in the region. Later, a vertical design spectrum for the Iranian plateau based on V/H ratio is proposed. At the end, using a calibration technique that can convert the horizontal uniform hazard spectrum to the design code horizontal spectrum is used to find the disgn response spectrum for vertical component of earthquake for Iranian plateau.},
Keywords = {Vertical component of earthquake,Vertical-to-Horizontal Spectrum Ratio,Seismic hazard analysis},
volume = {17},
Number = {4},
pages = {89-100},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5769-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5769-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Approximate Nonlinear Seismic Evaluation of Frame Buildings by Static and Dynamic Analysis Methods and Comparison with the Exact Solutions},
abstract ={Performance-based earthquake engineering requires accurate estimation of the seismic demand and capacity of structures. In recent years, various kinds of nonlinear static and dynamic analyses have been developed for the seismic evaluation of structures. Nonlinear dynamic time history analysis method is not only very time consuming, but also needs a proper skill and proficiency in order to interpret its results. For the performance evaluation of the structures, the speed and also the precision of conducting different analyses are very significant criteria. This issue has led to the creation of various new methods based on the principles of nonlinear and incremental static and dynamic analysis. One of the methods that has been proposed to tackle this task is incremental dynamic analysis (IDA). This procedure requires non-linear time history analyses (NL-THA) of the structure for an ensemble of ground motions, each scaled to many intensity levels, selected to cover a wide range of structural response; all the way from elastic behaviour to global instability. From the results of such computation, it is possible to determine structural capacities (or ground motion intensities) corresponding to various limit states; immediate occupancy (IO), life safety (LS), or collapse prevention (CP). Another approach to reduce the computational effort required for IDA is to estimate seismic demands for the practical structures by modal pushover analysis (MPA), an approximate procedure, instead of non-linear RHA. Thus, each of the many non-linear RHA required in IDA is replaced by a MPA. In addition, a more recent proposed method logically combines two different techniques, IDA and MPA is employed, presented by modal incremental dynamic analysis (MIDA). Using MIDA procedure, simple approximate curves that present a realistic linear and non-linear seismic behavior of the structure headed for the calculation of the damage measure (DM) due to the applied scaled level of earthquakes can easily be extracted. In this study, the capability, limitation and precision of MPA in comparison with NL-THA and also MIDA in comparison with IDA method are evaluated. For this purpose, two steel building models of 5 and 15-story with special moment resisting frame (MRF) in X direction and simple frame with X-bracing in Y direction has been designed. Furthermore, seven far field earthquake records are used for nonlinear analyses. In the current article, acceleration spectral intensity of the first mode of vibration with 5% damping, i.e. Sa(T1, %5) factor, are used as of intensity measure (IM). The story deflection and story drift are chosen as of the most important DM parameters to estimate the seismic vulnerability of structures in design practice. Comparison of the numerical results reveals that the MPA method has good accuracy in building seismic demands evaluation for 5-story frames (MRFs and braced frames) and 15-story MRF. However, no exact response is obtained for 15-story braced frame, considering the first three vibration modes of the structure. It is also shown that the results from MIDA simple method compares favorably to the IDA method. Thus, MIDA can be served by design engineers for seismic analysis in order to evaluate structural performance due to its relative simplicity and minimal computational effort.},
Keywords = {Seismic evaluation,Nonlinear behavior,Approximate analysis,Exact analysis,Steel building},
volume = {17},
Number = {4},
pages = {101-112},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-2457-en.html},
eprint = {http://journals.modares.ac.ir/article-16-2457-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Asakereh, Adel and Ahang, Masou},
title = {Predicting Maximum Horizontal Displacement of the Wall and the Maximum Tensile Force in Reinforcements for Geogrid Reinforced Soil Wall under Overturning Mechanism},
abstract ={Soil reinforcement is a new technique to improve the mechanical properties of soil. Geosynthetic reinforced soil walls are usually designed based on limit equilibrium methods, ignoring the effects of foundation, reinforcement stiffness, facing, and other parameters. However, design procedures do not consider the deformation of the walls explicitly. Recently, numerical methods are used for the design and analysis of reinforced soil walls, and the programs written on this basis are used. Usually in limit methods, design of reinforced soil structures control for external stability or total stability or internal stability. After design of reinforcement elements, the overall stability of wall, i.e. overturning, sliding, and bearing capacity should be controlled. But in numerical methods, stress distribution and deformation can be achieved in reinforced soil walls. In this study, the finite difference method is used to perform analysis. According to the deformation manner of the wall and boundary conditions imposed on the structure in the reference study, so that the wall is joint at the heel (wall cannot slide) and taken into account its foundation in the rigid (insufficient bearing capacity does not happen), it can be said that obtained results of this modeling are used only for the overturning mode. In this numerical study, the effect of various system parameters on the performance of the wall, especially the maximum tensile force in the reinforcements and the horizontal displacement of the wall, is merely investigated for the external overturning instability mode. The important parameters of reinforced soil wall structure were studied including the reinforcement stiffness (J), the backfill soil friction angle (∅), the elasticity modulus of backfill soil (Es), the facing wall rigidity (EI), the reinforcement length (L), and wall height (H). Among investigated parameters, the most important parameters effective on the amount of deformation of the wall and maximum tensile force in reinforcements are reinforcement stiffness (J) and backfill soil friction angle (∅) regarding the material properties, respectively; other parameters do not have significant effect on the cases studied. The effect of stiffness on the maximum tensile force in the reinforcements is minimal and negligible. In the wall geometry which includes the reinforcement length (L) and wall height (H), the reinforcement length was the most effective and the most important factor to design reinforced soil walls. Based on the numerical results, the best range of L/H ratio to design reinforced soil walls is between 0.5 and 0.8 since for L/H ratio equal to 0.8 and more, the horizontal displacement of the wall is considered almost the same. Due to the importance of the project and the cost, it is suggested to consider L/H equal to 0.7. In this numerical study, curves are provided for predicting the maximum horizontal displacement of the wall and the maximum tensile force in the reinforcements. The numerical analyses show that there is a particular pattern between the maximum horizontal displacements of the walls and maximum tensile forces in the reinforcements. The results are presented in the form of graphs; using these graphs, the maximum horizontal displacement of the facing wall and the maximum tensile force in the reinforcement for walls with different heights can be predicted.},
Keywords = {reinforced soil wall,maximum tensile force in the reinforcement,maximum horizontal displacements of the wall,finite difference analysis},
volume = {17},
Number = {4},
pages = {113-126},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8220-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8220-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Farhoudi, Mahdiar and SalehiNeyshabouri, Seyed Ali Akbar and Safarzade, Akbar},
title = {Two-Phase Numerical Simulation of Flow Pattern in Three-sided Spillways, Considering Scale Effect},
abstract ={Regarding significant reduction in costs and operating problems, three-sided spillway in comparison with other spillways, attracts crucial attention of designers of these structures. Three-side spillways are a type of outlet works at dams that despite their hydraulic limitations and construction problems, under specific topographical conditions selected as one of the best options in storage dams. This spillway is applicable in areas concerned with limitation of available space for overall width of spillway and where excess volume for flood overload. Also when modification and capacity increase in existing spillways are necessary, this structure is recommended. On the other hand, inappropriate conditions in water channel, such as flow turbulence and impact of water on bed and lateral walls of channel result in poor performance of these structures. In the present study, firstly 3D flow pattern of a U-shaped spillway, the channel and the end sill have been evaluated using computational fluid dynamics software (FLOW-3D). RNG k-ɛ model was implemented for simulation of turbulence. Comparison of numerical results with experimental data showed that this model has a good ability to predict three dimensional flow patterns over this kind of spillways. Hydraulic performance with targeting to reduce pressure fluctuations in side channel is an important issue in this type of spillways design. Regarding important effect of air entrance in hydraulic structures, two-phase analysis has been performed in this study. Numerical results show that two-phase analyses have a better performance compared to one-phase simulations. Studies show that by changing the inlet flow rate, the maximum error in the estimation of water level and pressure profiles at bottom of the channel occurred at low discharges. Also the maximum numerical error in computing observed in the area where bulge is. Then, taking into account the actual dimensions of the model, scale effects have been studied on physical model scales. The findings have some major implications of civil, environmental and sanitary engineering, because most hydraulic structures, storm water systems and water treatment facilities operate with Reynolds numbers within ranging from 106 to over 108. In a physical model, the flow conditions are said to be similar to those in the prototype flow conditions if the model displays similarity of form, similarity of motion and similarity of forces. The present results demonstrated quantitatively that the dynamic similarity of two-phase flows cannot be achieved with a Froude similarity unless working at full-scale. So that physical models are not good at predicting air entrainment and the amount of air entering is dependent on Reynolds number and does not follow Froude similarity. The largest amount of free surface profile variation due to aforementioned reason has been observed in air entrance and bulge formation zones. This variation decreases as flow moves toward downstream or as discharge value increases.},
Keywords = {Flow 3D,numerical simulation,Three-sided spillway,two-phase flow,Scale effect,Flow 3D},
volume = {17},
Number = {4},
pages = {127-140},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1179-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1179-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Ghassemieh, Mehdi and hasanisokhtesarae, mohamad and bastami, mortez},
title = {Suitable Remote Range Strong Motion Accelerograms for three-dimensional non-linear analysis for Tehran,Iran},
abstract ={In regions that are susceptible to earthquake occurrence, designing large and engineering developed structures such as tall buildings, dams and bridges most often requires quantitative dynamic analysis. Engineers discuss important questions on possible magnitude of earthquake in the zones under construction and require knowledge on the movements or the spectrums enforces and/or defining parameters. Time history analysis is the most natural analytical method compatible with the physical behaviors in the course of earthquake in a way that structures are performed by including the effects of earth acceleration as a function of time being applied in the structural base. The accelerograms which are used in analyzing the chronological history in determining the impacts of earth movement must reveal the actual movements of earth in the construction site of the structure during earthquake; As a result, selecting accelerogram is very important in analyzing the chronology. Unfortunately, the point that suitable records must be selected with respect to the conditions that govern seismic source, the geological characteristics, tectonic distance from fault and the largeness of the zone is usually neglected. Our country is located in one of the most active seismic regions in the world. According to the scientific information and documents, Iran is one of the riskiest regions of the world and is exposed to serious damage from earthquake. In the recent years, there has been an earthquake with large physical and financial casualties in one of the regions of the country once every five years in average. Presently, Iran is on top of the list of countries where earthquake is associated with life casualties. It is very difficult to fully prevent damages caused by high magnitude earthquakes. This is especially important in the city of Tehran with the very large population that lives in it, and is encircled by several active faults. The main goal of this research is to prepare a suitable list of remote range strong motion accelerograms to be used in nonlinear analysis in Tehran. The main focus of this research is to study all parameters that are effective in selecting suitable strong motion accelerogram in Tehran and for this purpose, 1000 strong motion accelerograms from earthquakes that occurred in Iran between 1978 through 2007 were studied and the entire parameters effective in selecting suitable strong motion accelerograms for the city of Tehran including distance, magnitude, frequency contents, earthquake mechanism, soil and specifications of earth strata were reviewed. Ultimately, a suitable list of strong motion accelerograms is presented to be used in nonlinear three-dimensional analysis. To achieve this goal, the geological and geotechnique features of the region were studied. In addition, the mechanism of active faults in the region were studied as well and by considering the parameters of magnitude, the focal depth, the distance of registry stations to the earthquake place, the geology studies of the records registry stations, mechanism and the frequency contents of a series of the accelerograms are suggested to reveal the actual movement of earth in Tehran as much as possible; if modeling and chronological history analysis are bi-dimensional, it will be possible to use 28 categories alongside and orthogonal with the faults in the suggested list. It should be noted that to analyze the chronology, only those accelerograms were used which could be scaled with the spectrum of the standard plan of the region and prove compatible with the frequency period of the structure. Minimum moment magnitude in the mentioned list is equal to 5.6 and maximum moment magnitude is 7.4. The mean magnitude in this list is 6.45. The mean maximum earth acceleration for the list was equal to 0.191g. The dominant mean period in the list is 0.64 seconds. The dominant frequency in this collection of accelerogram includes a large frequency range; therefore, suitable stimulation could be anticipated from this list for various structures.},
Keywords = {Dynamic Analysis,List of Recorded Accelerograms,Acceleration,Far field,Actual movements of earth},
volume = {17},
Number = {4},
pages = {141-152},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1002-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1002-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Kamgar, Reza and Khatibinia, Mohse},
title = {Multi-objective Optimization Design of Tuned Mass Damper System Subjected to Critical Excitation},
abstract ={Controlling the maximum acceleration and displacement of the roof within the acceptable range is important and essential. In order to control structures, a number of control systems have been introduced that are categorized into four system including active, passive, semi active and hybrid system. One of the most used passive systems is the tuned mass damper system which is placed on the roof of structure for controlling the behavior of building. In addition, the optimization of structures subjected to the earthquake load is an essential task for the safe and economic design of structures. It must be noted that earthquakes are random phenomena and the precise prediction of forthcoming events is a hard task. However, in seismic design codes, the static and modal seismic methods for the seismic design of structures are adopted by the design spectrum produced based on previous earthquakes. Hence, in order to overcome this problem, the concept of critical excitation as a robust method has been presented and developed to generate worst–case critical excitations. The critical excitation method have been presented in the framework of an optimization problem to maximize the structural responses subjected to some constraints. In this paper, an effective method is presented to determine the optimum values for the parameters of the tuned mass damper system subjected to critical earthquakes. The critical earthquakes are unique and are computed based on the dynamical properties of the structure. For this purpose, based on the obtained information from the past occurred earthquakes the critical earthquakes of a ten story shear building are established subjected to the constraints. The constraint scenarios include some computable properties of the ground motion such as energy, peak ground acceleration an upper bound Fourier amplitude spectrum. In fact, in this stage, to compute the critical earthquakes an inverse nonlinear constraint optimization problem must be solved for each time step. Then, the building equipped by a tuned mass damper system at roof of the structure (controlled building) is considered and the optimal design of tuned mass damper subjected to critical earthquakes are implemented. The maximum absolute displacement and acceleration of the roof are considered as the objective functions. Finally, among the computed earthquakes, one of them which produces the maximum objective functions is selected as the critical earthquake. In the optimization procedure, the mass, damping and stiffness of the tuned mass damper (TMD) system are adopted as the design variables. Multi-objective particle swarm optimization method is used to optimize the parameters of the tuned mass damper system. Since, the optimal design of the tuned mass damper system is presented as a multi-objective optimization problem, a set of optimal solutions are obtained. Numerical examples demonstrate the ability and efficiency of the proposed method in the optimal design of the tuned mass damper system subjected to the critical earthquakes. In addition, the numerical results show that the maximum absolute values of the displacement and acceleration of the roof efficiently decreases when the building is controlled by the optimum tuned mass damper system. Also, the results show that the severe earthquake needs a bigger mass for tuned mass damper in order to control the displacement and acceleration of the roof.},
Keywords = {Critical excitation,Tuned mass damper,Multi-optimization,Particle swarm optimization method},
volume = {17},
Number = {4},
pages = {153-164},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-10935-en.html},
eprint = {http://journals.modares.ac.ir/article-16-10935-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Karimian, Erfan and o, m},
title = {Application of Edge Based Smoothed Finite Element Method in Solution of Seepage and Foundation Settlement Problems},
abstract ={Smoothed finite element method (SFEM) was introduced by application of the strain smoothing technic in the conventional finite element method (FEM). The strain smoothing technic was previously used in mesh-free methods to overcome the numerical instabilities due to nodal integration. SFEM has three main types: 1-Cell-based SFEM (CSFEM), 2-Node-based SFEM (NSFEM) and 3-Edge-based SFEM (ESFEM). In these methods, problem domain is first discretized into a mesh of elements, similar to the FEM, and then based on these elements, domains are created to perform the strain smoothing operation on them. These domains are called “Smoothing Domains”. The difference between SFEM types is in the method of creating these smoothing domains. Different smoothing domains, can give results with different qualities. Among them, the edge-based method can give results that are ultra-accurate and super-convergent. Due to their interesting features, SFEMs have been used to solve different problems. Problems such as, mechanics of solids and piezoelectrics, fracture mechanics and crack propagation, heat transfer, structural acoustics, nonlinear and contact problems, adaptive analysis, phase change problem and many more. In this paper, first idea and formulation of SFEM is reviewed, with special consideration on the edge-based method. Detailed instructions are given for creation of edge-based smoothing domains, and strain and stiffness matrices for this method are derived. After that, the algorithm for creation of a SFEM code is introduced. Based on these formulations and algorithm, an edge-based smoothed finite element code is created, that is used for analysis of some numerical examples. Two problems, based on two different practical geotechnical engineering applications, are solved using the ESFEM and also FEM with 3-node and 6-node triangular elements. Using same mesh for all three methods, makes comparison possible, and performance of the ESFEM will be investigated. First problem, is a steady state seepage problem, where seepage below a sheet pile barrier is modeled, with the assumption of plane strain condition. Since there is no analytical solution for this problem, FEM results using 6-node triangular elements are considered as the more accurate results for comparison. Investigating the results reveals that implementation of the strain smoothing technic in FEM using 3-node triangular elements, can make the results closer to those of the FEM using 6-node triangular elements, while the degrees of freedom remain constant. Edge-based smoothed finite element method can give results for steady state seepage problem, that have errors less than half of the conventional FEM results errors, with the same mesh and number of degrees of freedom. The other problem, is calculating the elastic settlement of a circular foundation, to investigate the performance of the ESFEM in axisymmetric problems, compared with the FEM. Again, the problem is solved using three methods: ESFEM, FEM with 3-node triangular elements, and FEM with 6-node triangular element, with the latter as the most accurate. Surface deformation of the problem domain, after imposition of the foundation load is studied. It is seen that ESFEM results match the FEM results. A closer look reveals that the ESFEM results for settlement of the foundation, is closer to the FEM results using 6-node triangular elements, than the FEM using 3-node elements and are more accurate.},
Keywords = {Smoothed Finite Element Method,finite element method,Steady State Seepage,Foundation Settlement},
volume = {17},
Number = {4},
pages = {165-174},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1194-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1194-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {m.nikbin, iman and Javadi, Shim},
title = {Assessing absolute maximum dynamic response of a single span beam acted upon by an accelerated moving object},
abstract ={In structural dynamics, loads having varying positions has been broadly studied. Such loads are so called moving loads which appears in various applications in industry. High speed machining systems, overhead cranes, cable ways, pavements, computer disc memories and robot arms are a few examples of moving load dynamic problems. Vibration of bridge structures subject to moving vehicles is often referred to as an application of moving load problems. A great number of researchers proposed numerical and analytical methods to deal with the vibration of solids and structures under travelling loads. A famous classic approach in the simulation of moving loads is the moving force. In moving force model, a constant traveling force is assumed to act upon the base structure. However, this assumption yields to reasonable structural analysis if the mass of the moving object is negligible. Nowadays, with ongoing advances of transportation technology, the mass, speed and acceleration of moving vehicles are notably increased. In this regard, during the last few decades, many researchers showed that the moving force is no longer valid for large moving masses. Therefore, the moving mass simulation has been proved to be closer to the physical model of vehicle bridge interaction. As a common practice, bridges carrying moving vehicles has been assumed as vibrating beams excited by point moving masses. It has been very customary to consider the midspan or center point of the base beam as the reference point in order to assess the maximum dynamic response of the structure under moving mass; therefore, most of the existing computed design envelopes are related to the values occurring at the midpoint of the structure. However, the location of the maximum values occurrence is not necessarily at midspan. To shed light on this issue, in this research an analytical-numerical method is established to capture dynamic response of an Euler-Bernoulli beam traversed by a moving mass. Most of the available literature on moving load problem is concerned with the travelling loads having constant speeds. To remove this restrictive presumption, in this paper, the considered moving mass is assumed to move at non-zero constant acceleration. The beam is considered to be undamped and initially at rest. The moving mass is assumed to maintain full contact condition with the base beam while sliding on it. By exploiting a series of continuous shape functions having time varying amplitude factors, a norm space is provided by which the beam spatial domain is discretized. The problem is then transformed into time domain for which a time integration method is utilized. Absolute maximum dynamic response of the supporting beam under the passage of accelerated moving mass is extensively sought over the beam length. In this manner, whole beam length is being monitored for the maximum values at each time step of time integration procedure. The beam absolute maximum dynamic response is comprehensively computed considering different mass ratios and extensive range of linearly time varying velocities. Parametric studies are carried out on the absolute maximum values of dynamic flexural moments and deflections and compared to those captured at midspan. Finally, it highlighted that the midspan of the beam cannot be a valid reference to obtain the true maximum deflections and flexural moments of the base beam.},
Keywords = {Moving mass,Euler-Bernoulli beam,dynamic response,normalized maximum dynamic response},
volume = {17},
Number = {4},
pages = {175-186},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7261-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7261-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Mohammadi, Yaghoub and Seifollahi, Fari},
title = {The Effect of nano-silica and polypropylene fibers on mechanical properties and durability of normal and light weight concretes},
abstract ={Over the course of time into the 21th century, concrete has been known as one of the most high usage materials in the construction industry. As a consequence, trying to produce light concrete is an active and developing area within the new field of construction science. This technology consists of lowering the whole weight of structure by using new bulding techniques, new materials and optimizing ways of manufacture. Lowering the weight not only economizes on the expenses, time and energy but also decreases the damages of earthquakes. Furthermore, it keeps the constructions safe and minimizes the damages resulting from the overweight of the structure during different waves of shocks and aftershocks. In spite of considerable amount of compressive strength, low tensility strength and relatively high fragility of the concrete, there are limitations in using it in some parts which are partially or fully under forces of tention in different parts of structures. This fundamental defect of concrete in practice can be eliminated by reinforcing it through using steel tabs in the direction of traction forces. Having in mind that the armature just constitues a small part of the whole cross section of the structure, it will not be correct to conceive of the cross section of concrete as an isotropic and homogeneous surface. In recent decades, in order to come up with the isotopic condition and decrease the fragility, weakness and retrogression of concrete new techniques and trends of applying slender fibers running through the internal section of the bulk of concrete has become prevalent and common practice. The concrete containing nano materials compared with the normal concrete affected by nono chemical materials with cement particles and clcium hydroxide crystals which exist in cement, has a severe effect on the performance of concrete composites while such mixtures come into each others’ contact. In this study,we examined the effect of Nano-silica and polypropylene fibres on mechanical properties and durability of normal and light weight concretes. In the design of light weight concrete, lecalight weight aggregates were used. More than 384 cubic and cylindrical samples were made based on ASTM standards and compressive strenght, indirect tensile strength, ultrasonic and electrical resistance experiments were done. The results of the experiments showed considerable increase in mechanical characteristics and durability of normal and light weight concretes. Nano-silica contributes to the proper spread of the fibers. Compressive strength, indirect tensile strength, and the dynamic elasticity module of the ordinary concrete were higher than those of the light weight concrete, while the electrical resistance of the light weight concrete was higher compared to the corresponding samples. Compressive strength and indirect tensile strength increased to 71 and 55 percent in normal concrete and to 43 and 47 percent in light weight concrete respectively. Considerable increase in electrical resistance indicates high durability of these kinds of concretes. Of course, economic considerations of using nano-silica and polypropylene fibers require special attention. Finally, the right amount of utilization of the polypropylene fibers and nano silica were determined in order to achieve normal concrete and light weight concrete with optimal properties.},
Keywords = {Nano-silica,polypropylene fibers,mechanical properties,durability,light weight concrete},
volume = {17},
Number = {4},
pages = {187-198},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9247-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9247-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {dahrazma, behnaz},
title = {Effects of Soil Washing by Fe3O4 Nanoparticles in the Batch and Continouse Flow Configurations on the Physicochemical Characteristics of Soil and Nanofluid},
abstract ={Remediation of contaminated soil by heavy metals is an important environmental issue which attracted many attentions and was evaluated by several methods. It is highly desirable to apply suitable remedial methods to reduce the risk of heavy metal contamination in soils. Development of new low-cost, efficient and environmental friendly remediation technologies is the main goal of the recent research activities in environmental science and technology. Using nanotechnology in removal of environmental pollutions is of modern and applicable methods. One of the early generations of nanoscale technologies in the field of environment is the use of iron nanoparticles as a ground for sorption of pollutants. These nanoparticles are nontoxic, inexpensive, and very strong absorbents.The aim of this study was to assess the effects of cadmium removal by soil washing with iron (III) oxide nano particles (Fe3O4), stabilized with Polyacrylic Acid (PAA) as nanofluid, on physicochemical characteristics of nanofluid and soil in two defined systems including batch and continuous flow configurations. For this purpose, after complete removal of Cd from the soil in both systems under the optimized conditions, the effects of removal on the physicochemical characteristics of soil and nanofluid including pH, electrical conductivity, and total dissolved solid were assessed. The results of XRD and SEM of soil samples and also zeta potential and size distribution of nanofluid, before and after the removal were investigated. To ensure the absence of other pollutants and elimination of any interaction between soil pollutants, the soil was prepared with clean standard materials and afterwards it was contaminated with cadmium solution prepared by cadmium nitrate. The optimum conditions for cadmium removal in the batch system was as follows: nanofluid concentration=500 ppm, pH=6.5, contact time=24 hr and the ratio of contaminated soil mass (gr) to nanofluid volume (mL) =1:150 . completely Cd removal in continouse flow configuration obtained in the following conditions: nanofluid concentration=500 ppm, pH=6.5, contact time=24 hr, and the flow rate =0.5 mL/min. Cadmium content in the nanofluid after remediation was determined with UV spectrophotometer by using APDC complexes in Tween 80 media. As per the results of this study, pH of the soil samples in the both batch and continuous flow configuration increased from 7.8 to 8.55 and 8.35 respectively. pH of nanofluid increased from 6.5 to 6.8 in the continuous flow configuration and 7.59 in the batch system. EC and TDS of the nanofluid decreased from 1.66 mS/cm and 1110 mg/L to 1.049 mS/cm and 699 mg/L in the continuous flow configuration and these parameters also reached respectively to 0.952 mS/cm and 635 mg/L in the batch system. Soil washing using Fe3O4 nanoparticle did not changed remarkably EC and TDS of the contaminated soil. Nanoparticles size with highest frequency in nanofluid before removal was 205 nmand after Cd removal reached to 23 nm and 29 nm in the continuous flow configuration and batch system respectively, which was an indication of the sorption of nanoparticles with grater size to the soil during the soil washing process. Zeta potential values of influent and effluent of nanofluid from continuous flow configuration and batch system were -61.5, -51.3, and -37.4 mV respectively. The structural changes of soil samples after removal in the both systems were assessed by XRD and SEM tests which confiremed the sorption of nanoparticles through the soil washing.},
Keywords = {Fe3O4 Nanoparticles,Soil Washing,Cadmium Removal,Physicochemical Characteristics},
volume = {17},
Number = {4},
pages = {199-212},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1452-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1452-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {MOMENI, KOMEIL and Madandoust, Rahmat and Ranjbar, Malek Mohamm},
title = {Assessment of concrete core strength with and without steel bars},
abstract ={The concrete compressive strength is a suitable index to ensure the quality of concrete while the construction is underway. The core samples, which represent the potential strength of concrete, are prepared, cured, and tested according to the relevant standard codes and specifications. On the other hand, determination of the actual strength of concrete in a structure is not easy because it depends on the history of the curing procedure, the adequacy of concrete compaction, and the casting method. Therefore, the question that has always attracted the attention of designers is if the standard test specimens can represent the in-situ strength of concrete. Arriving at the answer to this question becomes even more important when the strengths of standard test specimens are lower than the specified strength. In this case, either the strength of concrete in the structure is lower than the design value or the specimens do not actually represent the concrete strength in the structure. In such cases, the problem would be addressed by drilling and testing some core specimens from the suspected structural member. In addition, there may be no standard specimens at a late age, and it may be necessary to determine the current strength of the structure.Concrete core test is always regarded as an important issue in the area of concrete industry to evaluate the in-situ concrete strength, and sometimes it becomes the unique tool for safety assessment of existing concrete structures. Core test is, therefore, introduced in most building codes. The presence of rebar in the cores affects the results of testing; accordingly, some codes specify that no bars are allowed to be present in the cores, while others account for the bars by introducing a correction factor. In the present experimental research, the parameters that exert significant effects on the strength of the cores containing rebar are examined. To that end, 112 plain and reinforced concrete beams with the bars of 10- and 16-mm diameter (with different arrangements) and water-to-cement ratios of 0.4 and 0.55 have been created. The beams have been kept and cured under air-dried conditions. In order to perform the compression tests, 988 concrete cores of 7.5- and 10-cm diameters with aspect ratios of 1 and 2 have been drilled at 14, 28, and 56 days of age. In the majority of cases, as the water-to-cement content increases from 0.4 to 0.55, there is a larger amount of strength loss in the cores containing the rebar as compared to those without any rebar. The strength of the cores declines by increasing the concrete cover for the bars. For the cores containing a single bar, the reduction which is resulted in the strength in comparison to that of the plain concrete cores is more dramatic in the cores having a bar of larger diameter. On the other hand, the amount of strength drop increases by increasing the number of bars. The largest drop in the strength values, amounting to 23 percent of the plain-concrete core strength, is observed in the concrete cores having two 16-mm bars. Furthermore, the cores containing eccentric rebar show a greater reduction in comparison to the cores with no eccentric rebar.},
Keywords = {core tests,strength,corection factor,steel bar},
volume = {17},
Number = {4},
pages = {213-228},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5782-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5782-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Modification and improvement of equations to estimate the scour hole formation due to 2D wall jets using PSO algorithm},
abstract ={Abstract: The interaction between the jets and the loose beds may cause scour hole formation. The scour hole developments may cause structural instability of the structures and increases the damage probability of the structures. Hence the scour hole dimensions estimation is an important subject for engineers. Many investigators worked on the effective parameters on scour hole dimensions due to plane wall jets. They have presented many different equations to estimate the scour hole dimensions. The equations may be used on a specific range of the effective parameters. Using the width range of the available experimental data the appropriate equations are developed. Using the dimensional analysis the non dimensional parameters such as Froude densimetric, Reynolds number, non-dimensional form of the sediment size, standard deviation of the sediment mixture, tailwater depth, non dimensional form of the channel width and non dimensional form of the time were obtained. Authors tried to use an optimization procedure to develop the equations. As, generally, solving the optimization models is impossible using the analytical procedure, recently new metaheuristic methods are used to find the optimum results. So, in this research PSO algorithm was used to find of the unknown exponents and coefficients leading to the best result of proposed equations. Two different algorithms local PSO (LPSO) and Global PSO (GPSO) were used to find the unknown coefficients and exponents. Sensitivity analysis of the algorithms showed that the algorithms proposed different coefficients and exponents for different values population. Among the proposed coefficients and exponents one set of them are the best with minimum error. Comparsion between the experimental data and previouse prposed equations confirms strong scatter. Hence, in this type of problem using the metaheuristic algorithm and sensitivity analysis are recommended. The analysis of the results showed that the scour hole depth due to plane wall jets, is increasing funcions of densimetric Froude number, tailwater depth, time, and non dimensional form of the channel width. However, this parameter is a decreasing function of sediment gradation and non dimensional form of the sediment size. Similar trends were also observed for maximum ridge height formed at the downstream of the scour hole. The distance of the maximum height of the ridge is also an increasing function of densimetric Froude number, time, non dimensional form of the channel width, and Reynolds number of the jet. However this parameter is an decreasing function of standard deviation of the sediment mixture and tailawter depth. The sensitivity analysis of the effective parameters on scour hole dimension to find the more effective parameters were conducted. The latter analysis showed that Reynolds number, non dimensional form of the sediment size and non dimensional form of time has secondary effect on scour hole dimensions due to plane wall jets. However, the jet Reynolds number has the secondary effect on temporal variations of scour hole dimensions. The latter parameters were omitted from the effective parameters on scour hole dimensions without sensitive decreasing of equation accuracy.},
Keywords = {Scour,Plane wall jets},
volume = {17},
Number = {4},
pages = {229-239},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11876-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11876-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {mirtaheri, maseou},
title = {Effects of URM infill panels on the progressive collapse of steel structures with moment resistant frames},
abstract ={When one or more vertical elements of a structure fail due to defects in construction stages or over loading or etc., load distribution path of the structure changes and local failure arises in the damaged area. This kind of damage is not considered by engineers and can cause local collapse. The local collapse can spread vertically or horizontally to the other areas of the building if no alternate path exists to redistribute the loads. Therefore, limiting the local collapse in the damaged area is major idea to mitigate progressive collapse in the buildings. Nowadays, analyzing the structures which are designed based on the current standards, against progressive collapse and offering ways to improve and strengthen them is leading to part of the designing stages of the special buildings. Thus, some standards and codes in this field are being produced or updated. The most common method to analyze the structure against progressive collapse is the alternate path method. In this direct design method, the critical columns be removed immediately and stability of the remaining structure is investigated. But there is no references talk about the effect of lateral resistant of the infill panels. This is one of the simplifier assumptions which are used in numerical studies of progressive collapse phenomenon in structures indicate inconsistency between the numerical and experimental full-scale results. Unlike numerical studies, experimental studies showed that the structure remain stable even if more than one column removed. As a case study, in this research, a steel structure with 8 stories with moment resistant frame is analyzes and designed considering effect of unreinforced masonry infill panels (URM). URM infill panels in full contact with the frame elements on all four sides shall be considered as primary elements of a lateral force-resisting system. Recognizing this behavior, the stiffness contribution of the infill is represented with an equivalent compression strut connecting windward upper and leeward lower corners of the infilled frames. So, analytical macro-model based on the equivalent strut approach is used to simulate the effective infill panels. Potential of progressive collapse of the one of the peripheral frames is evaluated with the Opensees program based on the nonlinear dynamic analysis. Researchers found that linear static analysis might result in non-conservative results since it cannot reflect the dynamic effect caused by sudden removal of columns. So, time-history analysis should be applied to seek dynamical response of the structure. Results indicate that considering effect of the infill panels increase axial force of the columns and decrease bending moment of the beams and nodes displacements. So results are closer to the experimental studies and prove stability of the structure after column removal and increase resistant of the building against progressive collapse. As it distinct, modeling the infill panels in the analysis is complex and time-consuming, so in this research, the coefficients are proposed to apply to the load combinations instead of modeling the infill panels in order to closer the results together. The proposed coefficients are larger than one for columns forces and smaller than one for the beams forces.},
Keywords = {progressive collapse,steel moment resistant frame,masonry infill panels,nonlinear dynamic analysis,alternate path method},
volume = {17},
Number = {4},
pages = {241-250},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11944-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11944-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {},
title = {Effect of Rectangular Strip Roughness on Hydraulic Jump Characteristic in Diverging Rectangular Sections With FLOW-3D Software},
abstract ={The hydraulic jump phenomenon is one of the most common phenomena in open channels. Hydraulic jump is a transition state from supercritical to subcritical flow regime, which normally occurs in conjunction with hydraulic structures, such as spillways, weirs, and sluice gates. A hydraulic jump phenomenon serves a variety of purposes, for instance, to dissipate the energy of flow to prevent bed erosion and aerate water or to facilitate the mixing process of chemicals used for the purification of water. Stilling basins are one of the most common structures for energy dissipation of flow with high velocities.The stilling basin has been accepted to be the most powerful hydraulic structure for the dissipation of the flow energy. The size and geometry of the stilling basin affect the formation of flow patterns, which can be influential for hydraulic performance of the whole system. The depth of water after the jump is related to the energy content of the flow, and any reduction in energy content with increased energy dissipation in the jump will reduce the required depth of flow after the jump. Sometimes these basins are supplied with appurtenances that increase the overall roughness of the basins. This in turn increases the energy dissipation, decreases the sequent depth, and requires a shorter basin for the full development of the hydraulic jump. There are plenty of research studies in the literature regarding the classical hydraulic jump in the usual rectangular straight stilling basin, but less for the hydraulic jump in other cross section shape of basins. Expanding gradually basin with the rectangular cross section acts as two separate hydraulic structures including stilling basin and transition. In this type of structures not only the transition can be eliminated, but the length of the basin will be also much smaller than what is designed for the usual straight basins. Researchers’ studies show that divergence in stilling basins reduce the sequent depth and the length of the jump while increasing the energy losses compared to the classic jumps. In this research, numerical simulation of the hydraulic jump was performed in divergence rectangular sections, and compared with the results of the laboratory, making use of the FLOW-3D software and the standard k-ԑ and RNG k-ԑ turbulence models. The effects of rectangular Strip roughness on the specification of hydraulic jump were evaluated. The results showed that the standard k-ԑ turbulence model was able to predict the water level profiles in the hydraulic jump in divergence rectangular sections with appropriate and acceptable coincidence. Results showed that the mean relative error of water surface obtained from numerical model and measured values is about 3.55 percent. Also the numerical model showed the vortices that were accrued because of diverging walls as well as experiment investigations. The results show that creating the rectangular Strip roughness, reduces the sequent depth as much as 13.65 % and the length of the hydraulic jump as much as 11.39%, while increasing the energy loss as much as 9.12%, compared to Smooth divergent stilling basin. The results also show that creating the rectangular Strip roughness, reduces the sequent depth as much as 24.63 % and the length of the hydraulic jump as much as 17.64%, while increasing the energy loss as much as 14.46%, compared to the classic hydraulic jumps. Consequently, the use of roughness in stilling basins would be economical.},
Keywords = {Diverging Hydraulic Jump,Rectangular strip roughness,k-ԑ Turbulence model,FLOW-3D software},
volume = {17},
Number = {4},
pages = {251-262},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4350-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4350-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Nikpoo, Bahador},
title = {Quantitative solution of 2-D inverse elastodynamics problems using hybrid FDM-FEM and PSO},
abstract ={It is clear that, having a exact knowledge about the geometry and properties of the materials and the domain that engineering problems are involved are very important specially in structural health monitoring, geotechnical earthquake engineering and other related field in civil engineering; in many cases, it might be useful if a suitable inverse solution is applied in order to detect the characteristics of the problems domain. The main purpose of this paper is to development of the hybrid finite element- finite difference method for solving inverse elastodynamic and elastostatic scattering problems and combining that with particle swarm optimization algorithm as a quantitative approach fo solving these types of the problems. This hybrid method has been used in order to preparing the forward solution of the problems and by defining a suitable cost function and minimizing that using PSO algorithm, various kind of inverse problems are solved. In general, an inverse scattering problem can be solved using qualitative or quantitative approaches. In some branches of quantitative techniques, usually, a forward solution is required and then using heuristic algorithm, the goal will be achieved. In this study, a hybrid FE-FD method is used as forward solver (which has the flexibility of finite element method and low computational cost of finite difference method); so, the domain inside and outside of the inclusion will be dicretized using finite difference method and the boundaries near the inclusion will be discretized by finite element method, and in this condition, the solution will be more flexible near the scatterer. In each solution step, first the finite element will be solved and the results will be transferred to the finite difference code and when the result is prepared in it, again, the response of the problem will go to finite element region. In this research, at first, a geometry and related location will be assumes, randomly and then regarding that, using an OpenSees program code, the boundaries of the inclusion will be discretized and using the MATLAB program the related to finite difference region is discretized, then the results from these two codes will go and back until the response goes converge. Then, the PSO code which is developed in MATLAB will qualify the results and evaluate the cost function (e.g., the cost function is defined by minimizing the the error between the displacement that is from the main model and the predicted model), and if the cost function is large, the PSO algorithm will propose the new location and/or geometry of the inclusion and again, the loop will be repeated until the cost function be near the zero and the solution procedure will be terminated. In order to evaluate, the efficiency and accuracy of the proposed approach, several problems are solved, where this algorithm could find the location and geometry of the inclusions (e.g., regular and irregular inclusion), the non-homogeneity of the inclusion and also detecting the soil layers by both static and dynamic loading.; the results show a very good accuracy as well as efficiency of the proposed approach for solving inverse problems in bounded and smi-infinite domains.},
Keywords = {Hybrid FEM-FDM method,Particle Swarm Algorithm,Quantitative inverse problems,2D Elastodynamic},
volume = {17},
Number = {4},
pages = {263-275},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-9048-en.html},
eprint = {http://journals.modares.ac.ir/article-16-9048-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {HashemiJokar, Mehdi and mirasi, sohrab and Rahnema, Hossei},
title = {Determination of clayey soil compression index (Cc) using adaptive neuro-fuzzy inference system},
abstract ={Construction of buildings and structures causes to compact of soil particles and soil settlement. Hence, determination and prediction of soil settlement in the stability of structures, resulting from the applied loads, is necessary before construction. As a result of consolidation test that is relatively time-consuming and costly testing, compression index (Cc) is used to get the amount of settlement. In fact, soil settlement can cause extensive damage to a project in some cases. In order To prevent these damages, correct prediction can be useful for safe designing of structures. Cc may be as a function of various parameters such as initial void ratio of soil, moisture of liquid limit, moisture of plastic limit, plasticity index, relative density, and so on. By considering the longtime of consolidation test, researchers have tried to find relationship between these parameters and Cc from the past until now. For this reason they tried to connect Cc to other physical measurable properties of the soil. In the past, some researchers have indirectly tried to measure these parameters. In this regard, several empirical single-parameter approaches are proposed to estimate Cc. Due to non-linear relationship between Cc and relevant parameters, Adaptive Neuro-Fuzzy Inference System (ANFIS) has found as an application to solve such non-linear problems and cases where an accurate understanding of the problem is required. ANFIS is a multilayer feed forward networks that is combination of Fuzzy Inference System (FIS) and Neural Network (NN). NN has ability to learn the input and output data and FIS is also capable for map the input space to the output space. ANFIS is a powerful tool to solve complex and nonlinear problems using the two mentioned features and also language power of FIS and numerical power of adaptive nervous system. In this paper, Compression index (Cc) is modeled by ANFIS. Two ANFIS model were created by subtractive clustering (SC) and Fuzzy c-means clustering (FCM), respectively, and then trained. By data clustering, collection of training data is divided into a number of fuzzy clusters and each cluster representing the system behavior. The data were collected from the Soil Mechanics Laboratory of Mashhad city. ANFIS input parameters are taken according to the same parameters that commonly chosen in most of empirical models for determining Cc that easily determined in the laboratory. These input parameters include initial void ratio (e0), liquid limit (LL) and plastic limit (PL). The number of required iterations for training (Epochs) in two ANFIS model, neighborhood radius (ra) in SC and number of clusters (NC) in FCM are optimized using trial and error method. After the end of solving and optimization of ANFIS models, the SC-FIS model was found in ra = 0.25 and NC =18 and the FCM-FIS model was obtained in NC = 20 with highest accuracy for prediction. Results showed both ANFIS model have a high capacity and appropriate forecasting for Cc prediction with chosen inputs parameters. Compared to the SC-FIS model, FCM-FIS is conducted prediction with higher accuracy. Using presented ANFIS models, can be predict the Cc of soils whose characteristics are within the specifications soils that used in this modeling with high accuracy and do not need to conduct consolidation tests that are very time consuming and costly.},
Keywords = {ANFIS,compression index,Prediction,Subtractive clustering,Fuzzy c-means clustering,Adaptive Neuro-Fuzzy Inference System},
volume = {17},
Number = {4},
pages = {277-287},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6911-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6911-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Esnaashari, Mehdi and Ahmadi, Elmir},
title = {Effect of sea water on unconfined compressive strength of clayey soil stabilized with lime and pozzolan},
abstract ={Clayey soils usually have low bearing capacity, high compressibility, shrinkage and swell characteristics. Several methods have been adopted to improve the geotechnical properties of such soils. Soil stabilizing by chemical materials is one of the most common methods for treating fine grained soils. Lime has been used to improve some mechanical and plastic properties of fine grained soils since many years ego. In recent years some studies has been also carried out to investigate the influence of adding pozzolany materials on the geotechnical properties of lime – treated clayey soils. Geotechnical behavior of clayey soils depends on chemistry of pore fluid. When drinking water is used to provide the needed moisture of soil in the laboratory, it will be lead to incorrect interpretation in engineering properties of soil where specific water such as sea water is utilized. Therefore, if the undrinkable water has been used to provide soil moisture, it is necessary to examine the behavior characteristics of the materials by the same water. For example, presence of some sulphates in the soil stabilized with lime leads to problems such as reduction of strength and increase of swelling in clay. In this laboratory study, effect of sea water on strength of stabilized kaolinite has been investigated by conducting several unconfined compression tests. The specimens were prepared at fore percentage of lime and pozzolan (i.e.0%,1%,3%,5%) by weight of dry soil and distilled water and three saline water which were taken from Caspian Sea, Persian Gulf and Urmia Lake. for every combination ,weight of each material was determined exactly based on the optimum moisture content and maximum dry density which is obtained from the standard proctor compaction test. Clay and lime and pozzolan were mixed in dry condition properly and then water was added gradually. Afterwards, the mixtures were kept in plastic bags for 24 hours. Weight of each specimen was determined in accordance with given specific volume and obtained maximum dry density from compaction test. This weight was divided into four portion and each portion was compacted in 20 mm layer in a PVC mold . The specimens were cured in a oven having a temperature about 35 ֠ C for 3, 7 and 14 days. After each curing time a extruder was used to remove the specimens from the molds with constant rate vertically to avoid bending and formation of tensile cracks. Then the specimens were immediately tested under strain controlled at constant loading rate of 1.0 mm per minute , according to requirements of ASTM D 2166. For each combination , three specimens were examined to assure repeatability of results. The results of conducted experiments indicate that unconfined strength of samples without additives (lime and pozzolan) prepared by sea water are higher than specimens containing distilled water. For the samples containing Urmia lake water, the unconfined strength were higher than the other samples. Also, for the specimens in which additive has been used, the strength of the samples containing Caspian Sea and Persian Gulf water were more than that with distilled water and the strength of samples containing Urmia lake water was less because of differences in the concentration of salts existed in the water . Finally, the results show that water minerals are higher in Urmia lake water, Persian Gulf and Caspian Sea, respectively.},
Keywords = {Stabilization,Sea water,Unconfined strength,Clay},
volume = {17},
Number = {5},
pages = {1-12},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11205-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11205-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Esmaeili-Falak, Mahzad and Katebi, H. and Javadi, A and Rahimi, S.},
title = {Experimental investigation of stress and strain characteristics of frozen sandy soils - A case study of Tabriz subway},
abstract ={Temporary soil improvement techniques are considered among the most important geotechnical topics. Artificial ground freezing is considered to be eco-friendly, economic, safe and applicable for all types of homogeneous, loose and soft soils. By lowering the soil temperature below zero, the pore water of the soil freezes which leads to improved mechanical properties of soil; it increases the shear and compressive strength of soil, without entering any chemicals into the soil environment. In practice, artificial ground freezing consists of two parts; (i) formation of frozen body before construction or test (active step) and (ii) maintenance of the frozen body during the construction and test procedure (passive step). There are two methods for using artificial ground freezing; (i) open method and (ii) closed method. In the open method, liquid nitrogen is used for cooling. With the evaporation of the liquid nitrogen, the soil freezes and the nitrogen gas is released to the atmosphere. In the closed method, a brine is used which is connected to a refrigeration plant. The brine is circulated until the formation of frozen body. The brine used can be ethylene glycol or calcium chloride. One of the difficulties of studying frozen soils is the absence of triaxial compression apparatus for frozen soils in the national and international markets, because it is an unconventional test apparatus. In this research, a triaxial compresion apparatus was developed for testing of frozen soils in the geotechnical laboratory of the University of Tabriz. This apparatus was placed in a cold and insulated room with minimum heat transfer. The temperature of the room was monitored continuously. This triaxial apparatus for frozen soils was developed using a closed system that is connected to a refrigeration plant. In this study, void ratio, ice saturation and texture of soil were considered as constant parameters and temperature, confining pressure and strain rate were considered as variable parameters. The soil samples were remolded in the laboratory to represent the in situ soil in the line 2, station H of Tabriz Subway. The in situ soil was poorly graded sand and fully saturated. A special type of mold was designed for this research, that was composed of aluminum material with high heat transfer. The mold was insulated from top and bottom and it was rigid in radial direction. A series of unconsolidated undrained triaxial tests were conducted on samples of the frozen soil using the developed triaxial compression apparatus. The results show that, at constant confining pressure and strain rate, decreasing temperature leads to increase in the shear strength and modulus of elasticity of the soil. Decreasing temperature also results in the yield point of frozen soil occurring at higher strains. Also, at constant temperature and strain rate, increasing the confining pressure increases the shear strength and modulus of elasticity of the soil. At constant temperature and confining pressure, increasing the strain rate leads to a moderate increase in the modulus of elasticity and a significant increase in shear strength of frozen sandy soil. Furthermore, the results show that the poorly graded frozen sandy soil samples tested in this research program show softening behavior. All the stress-strain curves show a peak and a residual state.},
Keywords = {frozen soil,Tabriz subway,mechanical properties,Geotechnical parameters,stress and strain},
volume = {17},
Number = {5},
pages = {13-23},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7658-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7658-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Haddad, Abdolhosein and Parsa, M. and Nasrollahi, S.M.},
title = {Investigation of the behavior of cellular confinement unit (Geocell) under static loading},
abstract ={Geological and site investigations in the world indicates that there are too many fields with soft soil. The existence of such soils in construction sites of buildings may create numerous problems for the foundations, for example the circumstances of roads, foundations and etc. Symmetrical and unsymmetrical settlement of foundations in soft soil areas may destroy even best constructions. Three dimensional geosynthetics could significantly improve the performance of soil and reduce the costs compared with conventional methods. In this article the behavior of this system has been investigated under vertical load in granular soil for the gap between the applications and the design theories of reinforced base with geocell. Although the geocll system behavior and the effects of adjacent cells on central cell is one of the cases that has not been studied sufficiently. In this article, the results of the plate loading tests on geocell reinforced sand bases have been studied, and the behavior of three dimensional cellular unit and the effects of adjacent cells have been considered as well. The effective parameters include the diameter and the number of cells. The test sample was a wooden box with 90 cm length and width and 60 cm height filled with poorly graded granular sand. In this study, geocells have been created by sewing the non-woven geotextile in a symmetrical pattern and dimension, and cells diameter were 12, 15, 17.5 and 22.5 cm. The strain gages were attached in order to eliminate measurement errors. The loading processes were carried out by a steel loading plate with 15 cm diameter. In this investigation besides the considering the geocell behavior, the optional design parameter of this system has been considered with the purpose of decreasing the settlement. Also, the non-woven geotextiles has been sewed in a symmetrical arranged pattern and the behavior of one-cell and multi-cell geocell has been compared. In order to evaluate the failure mechanism of geocell, the novel method of strain gage installation in nonwoven geotextile has been used. The results include the bearing capacity, the soil surface and cells deformations under a vertical loading. The results indicate that the cells which have a diameter equal to the loading plate have better performance than the others. Also it has been clarified that the existence of adjacent cells with the diameter of 0.8 times the diameter of loading plate, are more suitable for eliminating the settlement. It is also observed that the cells which are smaller than the loading plate, encountered more deformation than the bigger ones. Also it has been proved that one-cell geocell with the diameter equal to the diameter of loading plate, improve the bearing capacity and base stiffness more than one- cell and nine-cell with diameter equal to 0.8 and 1.7 times of the loading plate diameter. It can be concluded that if the loading position was fixed, one-cell geocell wih diameter equal to foundation diameter is recommended. For moving loads (car load on road), geocell with diameter less than diameter of loading plate should be used.},
Keywords = {Geosynthetics,Geocell,bearing capacity,Membrane strain,Reinforced sand bed},
volume = {17},
Number = {5},
pages = {25-36},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7156-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7156-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Toopchi-Nezhad, Hamid and Panahian, Amir},
title = {A comparative study on the performance of tuned liquid column dampers (TLCDs) and tuned liquid column ball dampers (TLCBDs)},
abstract ={Tall buildings, due to their significant flexibility in horizontal direction, exhibit very limited inherent damping. As such, their resonance or near-resonance excitations induced by wind loads may result in lateral structural response values that exceed the serviceability limit states of the structure. A mass damper when attached on a tall building can significantly mitigate the near-resonance lateral response of the structure. Tuned liquid column dampers (TLCDs) which consist of one or more U-shaped vessels with partially-filled water are known as a common type of mass dampers. In the conventional type of these dampers, an orifice is located at the horizontal portion of the vessel to dissipate the energy of the oscillating liquid within the damper. In the new type of these dampers, the orifice is replaced by a coated steel ball that is immersed in water at the horizontal portion of the vessel to dissipate the oscillating energy of the liquid within the damper. The latter damper is termed as tuned liquid column ball damper (TLCBD). In this paper the performance of a set of different TLCDs and TLCBDs in response mitigation of a tall building (of 75-stories) under harmonic wind loads have been investigated. A large set of time history analysis runs have been performed to study the role of different damper design parameters on the lateral response of the tall building. The design parameters investigated in this paper include geometrical and mass properties of the liquid dampers, inherent damping of structure, and the frequency of input excitation. The outcome of analysis runs has been compared to highlight the cons and pros of TLCDs and TLCBDs in wind-response mitigation of the building. Results of this study indicate that both damper-types are effective in response mitigation of the original structure. The peak roof displacement is decreased by 50% to 88% as a result of using the liquid dampers in the structure. Given the mass and geometrical properties of dampers, the performance of TLCBDs will be superior to that of TLCDs in response mitigation of tall buildings. Based on the analyses conducted in this paper the attenuation of building deformations in a system equipped by a TLCBD is 5% to 25% larger than the case where the same system is equipped by a TLCD. However, the performance of TLCBDs is more sensitive to the frequency of input excitations. An increase in the mass of the damper, in both TLCD and TLCBD systems, results in an increased response mitigation. For instance, when the mass ratio of damper is increased from 1% to 5%, the peak lateral displacement of structure, depending on the type and geometry of damper, is further decreased by 30% to 50%. The length of the horizontal portion of the U-shaped vessel of the damper was found also to be significantly influencing the response mitigation efficiency of damper in both TLCD and TLCBD systems. When the length of the horizontal portion of the damper is increased from 0.5 to 0.9, the roof displacements experience approximately 30% to 40% further reduction.},
Keywords = {tall buildings,tuned liquid column dampers,tuned liquid ball dampers,vibration control,wind load},
volume = {17},
Number = {5},
pages = {37-47},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7246-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7246-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {javadirad, mohammad and shahrokhi, mahdi and rajaee, taher},
title = {Numerical Investigation of the number of baffles effect on the efficiency of primary sedimentation tank in true dimensions},
abstract ={Numerical Investigation of the number of baffles effect on the efficiency of primary sedimentation tank in true dimensions. Settling tanks of wastewater treatment plants are the most important components so that about one-third of the cost of a wastewater treatment plant construction is concerned to these tanks. In addition, the regulations referred to design of settling tanks are not enough. According to these, the adverse factors in settling tanks is very important to design and improve their performance. These factors in primary sedimentation tanks are including circulation zones, the phenomenon of short circuiting and non-uniform flow. One of the most important ways to improve flow conditions and increase the efficiency of settling tanks, is modifying the geometry of the tank through the installation of baffles. In this investigation, the effect of baffle structures on the hydraulic efficiency of primary sedimentation tanks has been investigated by three-dimensional numerical modeling in Flow-3D software. In this study, the optimum number of baffles is studied to increase hydraulic efficiency. Settling tank in true size and simplified model primary settling tank treatment plant south of Tehran. The geometry Specifications of tank include of length tank (L) from the main inlet to the overflow output of 60 m, a width of tank (W) 12.9 m, water depth in normal mode (H) 3 m. the input flow rate to the tank 650 l/s. Model geometry using AutoCAD software and three-dimensional shape is drawn. In this study, from three mesh blocks to mesh geometry model is used. All three of these blocks in all directions are fully in touch with and the type of are linked blocks. Intended for three blocks, the size of the mesh is selected respectively, 5, 7 and 10 cm monotonically in each direction. In numerical modeling, the turbulence model used to solve turbulent flow and to solve pressure the GMRES method is used. In addition, the VOF technique to show the behavior of fluid on free surface flow and FAVOR technique have been used to simulate surfaces and geometric boundaries. Verification of numerical simulation results with former experimental data properly acknowledges the numerical results. It is already known the optimal location of the first baffle. The results show that baffle causes the uniformity flow and increase removal efficiency of the primary sedimentation tanks. To determine the optimum number of baffles, the comparison results between no baffle tank and optimized cases with one, two and three baffle done. Using more baffles, in ideal conditions, causes suppression of the jet flow and more chances the suspended particles deposition. The addition of new baffles in suitable locations reduces the maximum velocity amount, the size of the circulation zones and kinetic energy and create uniform velocity vectors inside the settling zone. Volume circulation zones by using one, two and three baffles compared to non-baffle decreased 4.18, 4.44 and 4.56% of the total tank volume, respectively. Finally, the results of the FTC method for several cases indicated that using number of baffles lead to increasing the performance of the sedimentation tanks.},
Keywords = {Flow-3D,primary settling tanks,baffle,Flow-3D,hydraulic efficiency,sedimentation},
volume = {17},
Number = {5},
pages = {49-59},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-8438-en.html},
eprint = {http://journals.modares.ac.ir/article-16-8438-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Kheyroddin, Ali and Sharbatdar, mohammad and Hadizade, Omi},
title = {Experimental Evaluation of HPFRCC effect on behavior of coupled beams without diagonal and spiral reinforcement},
abstract ={HPFRCC is the materials including cement mortar, aggregate, and fibers which represent strain hardening within tensile load. The HPFRCC can be used in numerous cases such as seismic rehabilitation of structural members. One of the structural members is the existed coupling beam in coupling shear walls which is applied as shear fuse. Using the materials in the members can enhance ductility and energy absorption and also delays failure. This paper investigates a study on the effect of existence of diagonal reinforcements and spirals of diagonal reinforcements of the coupling beam. For this purpose, three prototypes of coupling shear walls with coupling beam were designed by HPFRCC with length-to-depth ratio of 2 and 1/2 scales. The first prototype is considered as reference and we use concrete with reinforcement design based on ACI 318-08 code. The other prototypes are built by HPFRCC with PPS fibers. But in one of them the spiral of diagonal reinforcements and in the other both spirals and diagonal reinforcements are omitted. In order to simulate the test set-up with real behavior, two strong walls were considered and cast at both sides of coupling beams. The rotation of these walls should be prevented, so in the experimental set-up, vertical small steel column in addition two strong steel roller were considered during tests. The several strain gauges were installed on longitudinal and diagonal and vertical bars to measure the strains during tests and particularly showing the displacement and load of yielding points of reinforcement. LVDTs were installed to measure the maximum displacement of the tip of beam and also to measure probable rotation. The drift if the ratio of the tip displacement of the specimen to the beam length and the ductility is the ratio of ultimate displacement to the yielding displacement and finally the energy absorption is the area under load-displacement cure for each separate cycle. Results are indicating of appropriate effect of HPFRCC concrete in enhancing ductility and energy absorption capabilities and it can also reduce diagonal reinforcements. In addition improved crack pattern and shrinkage of cracks represent an appropriate participation of fiber in increasing the shear capacity. Comparing these prototypes, it is found the one in which spirals were omitted load capacity، ductility factor، energy absorption and failure displacement capabilities have been increased 15%, 36%, 69%, 35%. And the prototype in which diagonal reinforcements were omitted, has decreased load capacity down to 36% and ductility factor and failure displacement have been increased up to 13%, 35% and finally energy absorption has no changes. The pinching loops of load-displacement hysteresis curves of specimens were compared and the results indicated that the pinching of HPFRCC specimen was reduce comparing to reference specimen even in case of omitting the spiral. The stiffness slope of each specimen was calculated and results showed that the HPFRCC specimen with diagonal bars had more 8 percentage but the stiffness of HPFRCC specimen without diagonal bars was reduced up to 60% comparing to reference regular concrete specimen. Elastic experimental shear capacity of specimens was about 5 times of elastic Design code (ACI) shear capacity because the shear capacity calculated by ACI is conservatively only based of diagonal bar shear capacity.},
Keywords = {"Coupling shear wall","Coupling beam","Ductility","High Performance Fiber Reinforced Cementitious Composites HPFRCC"},
volume = {17},
Number = {5},
pages = {61-72},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12061-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12061-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Rostamabadi, Massumeh and NajiAbhari, M},
title = {Comparison of the results of studies designed by Taguchi and full factorial methods for parametric investigation of flow pattern around spur dike},
abstract ={Full factorial investigation is necessary in the study of the hydraulic phenomena which are function of different variables with different levels. It is logical to use the full factorial method when the number of variables and their levels are low. However, sometimes due to lack of time and shortage of financial restrictions, using the full factorial method is not possible. The Taguchi method, which is used for design of experiments, uses the fractional factorial instead of full factorial. This method not only decrease the number of studies but also guaranties the correlated comparison of all variables. In this paper the Taguchi method is used for finding the optimized hydraulic parameters like length and location of spur dike in different Froude Numbers in 90 degree bend. Furthermore, the comparison between the Taguchi method and full factorial is done for the number of investigations, finding the optimized level for each parameter and the time needed for study. In order to get the results, the parameters of length, location of spur dike in 90 degree bend, and the Froude Number are considered with three different levels. The SSIIM numerical model is applied to simulate the studies designed by Taguchi and full factorial methods. The results show that the Taguchi method, could predict the optimum parameters only with 9 studies whereas with full factorial method 27 studies was necessary. Also, using Taguchi method leads to more than 66% decrease in the total running time. For studies designed by Taguchi method, the optimum value of length of spur dike is the as one designed by Full factorial method. Also, the length of spur dike is the most effective parameter on flow pattern around spur dike and the position of spur dike and Froude Number are next in rank, respectively. These results are the same for two methods used to design of studies. Using 9 studies designed by Taguchi method, investigation of the effect of other parameter such as the angle of the spur dike is possible without changing the number of studies, whereas 81 studies should be done by full factorial method. Full factorial investigation is necessary in the study of the hydraulic phenomena which are function of different variables with different levels. It is logical to use the full factorial method when the number of variables and their levels are low. However, sometimes due to lack of time and shortage of financial restrictions, using the full factorial method is not possible. The Taguchi method, which is used for design of experiments, uses the fractional factorial instead of full factorial. This method not only decrease the number of studies but also guaranties the correlated comparison of all variables. In this paper the Taguchi method is used for finding the optimized hydraulic parameters like length and location of spur dike in different Froude Numbers in 90 degree bend. Furthermore, the comparison between the Taguchi method and full factorial is done for the number of investigations, finding the optimized level for each parameter and the time needed for study. In order to get the results, the parameters of length, location of spur dike in 90 degree bend, and the Froude Number are considered with three different levels. The SSIIM numerical model is applied to simulate the studies designed by Taguchi and full factorial methods. The results show that the Taguchi method, could predict the optimum parameters only with 9 studies whereas with full factorial method 27 studies was necessary. Also, using Taguchi method leads to more than 66% decrease in the total running time. For studies designed by Taguchi method, the optimum value of length of spur dike is the as one designed by Full factorial method. Also, the length of spur dike is the most effective parameter on flow pattern around spur dike and the position of spur dike and Froude Number are next in rank, respectively. These results are the same for two methods used to design of studies. Using 9 studies designed by Taguchi method, investigation of the effect of other parameter such as the angle of the spur dike is possible without changing the number of studies, whereas 81 studies should be done by full factorial method.},
Keywords = {90 degrees bend,Taguchi method,full factorial,cost and time effective},
volume = {17},
Number = {5},
pages = {73-83},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4961-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4961-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Rezaifar, O. and AlizadehNozari2, M.},
title = {},
abstract ={},
Keywords = {},
volume = {17},
Number = {5},
pages = {85-95},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-33439-en.html},
eprint = {http://journals.modares.ac.ir/article-16-33439-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {zeini, maryam and Edrissi, ali},
title = {Analytical model of trip production in transportation network after disaster},
abstract ={Unexpected events always occur without any alert about where or when they will happen. According to history of earthquake in Tehran, Iran, the probability of a huge earthquake occurrence (about 7 Richter) is high. The Unpredictable human behavior in disasters can affect the performance of the transportation networks. Considering the specific effects of an earthquake on the travel demand (i.e. the influx of travel demand in a short period and chaotic behavior of the users of the transport network), the issue of post-earthquake travel demand needs to be investigated. Since people travel behavior would be quite different from the ordinary situation, this research proposes a method to estimate the demand based upon the interview survey. The goal of this study is to determine the trip purposes immediately after the earthquake and the factors affecting the individuals' decisions on their trip purposes. In most previous literatures, the majority of policies which have been modeled are based on unrealistic assumed demand. Many previous studies have acknowledged that more trip purposes in response to earthquake exist but few, if any, have examined it in-depth. For example, Since an earthquake cannot be predicted, in a study conducted by Chang et al. to estimate the post-earthquake travel demand, it is assumed that people will evacuate directly from their current locations immediately after earthquakes because under the no-notice earthquake scenarios, there is no time or considerably less time for people to return home or go to other places to pick up their relatives or friends [Chang et al. 2012] while most people will return to home to rescue their family [Hara, 2013]. This research developed discrete choice (Multinomial Logit) model to represent effective factors on travel demand behavior after 2 earthquake scenarios (Strong & weak) in a workday, with 4 trip purposes (rescue and Inquiry on Safety, return-to-home, evacuation and no-action). This study investigated on travel behavior after an earthquake, based on a statistical analysis on stated preference (SP) questionnaires which were answered by 364 interviews in Tehran. The survey data indicated that, 90% of people may prefer to make trips in order to return to home or to rescue survivals after a powerful day earthquake The collected data expressed that although, it is not expected to have a problem in transportation network after a weak earthquake, the statistics from this study represented that about 35% of people will travel with different purposes because of their fear and it should be considered that despite a moderate earthquake will not destroy transport infrastructures, heavy traffic congestion will cause an emergency situation in transportation network. The goodness of fit (ρ2 statistic) of the model was obtained 0.425 that is a fairly good indicator for the discrete choice models. The model has also predicted the trip purposes in 67% of the observations correctly. The results of the model show that the most effective factors on destination choice behavior are gender, age, travel time, magnitude of earthquake, house ownership and family number. Also unrelated education to the earthquake is not effective on people travel behavior. Informing people about probable open routs after earthquake in advance would help planners for disaster management.},
Keywords = {Behavior models,Travel demand after disaster,discrete choice models,Logit models},
volume = {17},
Number = {5},
pages = {97-108},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-7214-en.html},
eprint = {http://journals.modares.ac.ir/article-16-7214-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {SALARI, Morteza and Akhtarpour, Ali and ekramifard, AMIN},
title = {hydraulic fracturing in inclined clay core of a high rockfill dam, located in a narrow valley},
abstract ={From a statistical perspective, internal erosion and piping are from the main causes of failure in earth-rockfill dams. If these dams were located in a narrow valley, the steep slopes of the valley walls can cause increasing in stress transfer in the core. Therefore, the occurrence of hydraulic fracturing phenomenon in this kind of dams is more probable. Bidvaz dam is an earth-rockfill dam with a thin inclined clay core. The dam is located in the Northeast of Iran with a distance of twenty kilometers from the Esfrayen city. It has a height of 66 meters from the foundation and constructed in a narrow valley with a width of 40 meters on river bed and a wall slope of more than 60 degrees relative to horizontal direction. After about seven and a half years of starting first filling, a subsidence was observed at the upstream slope surface of this dam. The initial assessments, based on the data recorded in instruments which were installed inside the body and dam foundation, show at the lower level of the core and adjacent to left abutment, pore water pressure gradually has been increasing and finally reached to the reservoir water pressure, and at the same time effective stress with abnormal rate reduced to zero. These observations confirm the occurrence of internal erosion in the lower levels of the core adjacent to the left abutment. Due to the steep valley walls and noticeable difference of compressibility properties between the core and shell materials, it is expected occurring significant stress transfer in the core especially adjacent to the valley walls. Therefore, the hydraulic fracturing can be considered as a main cause initiating the process of internal erosion in this dam. The main objective of this paper is to assess the validity of this hypothesis. To achieve this purpose, this paper used a three-dimensional numerical model to simulate the behavior of the dam during construction and reservoir filling. This model has improved in the environment of a finite difference software, called FLAC3D. In the formulation of numerical model, the flow and mechanical equations have been solved simultaneously. The 3D model has been calibrated based on the recorded data from the instruments. With using a number valid suggested theoretical and empirical relationships, hydraulic fracturing potential have been calculated and the contour distribution of fracturing pressure at upstream side of the core has been presented. Also, the contour distributions of factor of safety against occurrence hydraulic fracturing phenomenon were determined for all of the suggested relationships at the upstream side of the core. The findings show that, as expected, the steep slopes of valley walls and the difference of the compressibility properties of the core and the shell materials caused significant stress transfer at lower parts of the core and adjacent to the valley walls. Moreover, the values of factors of safety against occurrence hydraulic fracturing phenomenon in upstream side of the core are less than unity near the walls. So, the hydraulic fracturing phenomenon is the one of the main causes initiating the process of internal erosion in the core.},
Keywords = {Embankment dams,Internal erosion,Arching,Hydraulic fracturing},
volume = {17},
Number = {5},
pages = {109-122},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6706-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6706-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Sadeghzadegan, Reza and Naeini, Seyed Abolhasan and Mirzaii, Ali},
title = {Evaluation of liquefaction resistance of unsaturated clayey sand},
abstract ={Soil mixtures such as clayey sands, silty sands, or clayey silts are among the categories of common natural soils observed in liquefied sites. The substantial amount of liquefactions discussed in previous contributions appeared to occur in sands containing plastic fines. In saturated soils, a notable amount of experimental studies were performed in past to examine the influence of fine content on the liquefaction potential of sands. In spite to the occurrence of liquefaction in unsaturated zones due to ground motions observed in past, there are few amount of experimental data that relate the potential of liquefaction with degree of saturation, Sr, specifically for soils with high degrees of saturations. In this article, the results of a series of careful laboratory test program is represented to determine the liquefaction behaviour of a sand mixed with a range of kaolinite including zero to 30 perect at elevated saturation conditions. This is experimentally achieved using a double-walled suction controlled triaxial cell specifically developed to conduct cyclic triaxial tests at high degree of saturations that were 80, 85, 90, 95 and 100 percent. The stress-strain behaviour of the soil is represented and compared with respect to the amount existing data available in the literature. The variation of excess pore water pressure during the cyclic loading indicate that, in saturated pure sand, the generation of excess pore water pressure was mainly occurred at higher cycle of loads while, in saturated specimens with 30% clay content, it is observed from the early cycle of loading stage. Also a change in suction of specimen during cyclic loading under undrained condition is observed. Due to the presence of air in unsaturated soil volume change occurs during cyclic loading. It can be observed that void ratio decrease while saturation ratio increases. Matric suction is almost constant during cyclic loading until pore air pressure reached at maximum value and by increasing pore water pressure matric suction decrease. During cyclic loading axial strain is small until pore water pressure reached the effective confining pressure. In this case sudden increase in axial strain occurs and liquefaction starts. Accordingly, it is seen that during the cyclic loads all tested specimens reached to the liquefaction state. The liquefaction potential within the soil is represented according to CSR20 and is found to be a function of fine content. It is appeared to be initially decreased within the increment of fine content up to 20%, and consequently, it is slightly increased with increasing the percentage of fines up to 30 percent. The above behaviour aspect was obvious in all the range of degree of saturation considered. Additionally, it is seen that at a given fine content, a slight desaturation of specimens caused a significant increment in the liquefaction resistance ratio (LRR) within the soil and was more evident within the decrement of the fine content. The trend observed for the variation of liquefaction resistance ratio versus the potential volumetric strains in pure sands appeared to be consistent to the logarithmic relationship as suggested in the literature.},
Keywords = {Liquefaction,Unsaturated Sand,Fine content,Degree of Saturation,Cyclic Triaxial Test},
volume = {17},
Number = {5},
pages = {123-133},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-2773-en.html},
eprint = {http://journals.modares.ac.ir/article-16-2773-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Sadrmomtazi, Ali and Tahmouresi, Behz},
title = {Evaluation of mechanical properties and durability of engineered cementitious composites (ECC)},
abstract ={One major weakness of concrete is the brittle fracture behaviour in tension, with low tensile strength and ductility. This brittleness has been recognized as a bottleneck hindering structural performances in terms of safety, durability and sustainability. The lack of structural ductility is due to brittle nature of concrete in tension which may lead to loss of structural integrity. Many infrastructure deterioration problems and failures can be traced back to the cracking and brittle nature of concrete. Many attempts have been made in the recent years to overcome these problems. To effectively solve these severe problems, a new type of composite, called as Engineered Cementitious Composites (ECC), reducing the brittle behaviour of concrete has been developed in recent decades. ECC with its flexible processing has emerged from laboratory testing to field applications leading to speedy construction, reduced maintenance and a longer life span for the Structures. Micromechanical design allows optimization of ECC for high performance, resulting in extreme tensile strain capacity while minimizing the amount of reinforcing fibers, typically less than 2% by volume. Tensile strain capacity exceeding 5% has been demonstrated on ECC reinforced with polyethylene and polyvinyl alcohol (PVA) fibers. Unlike ordinary cement-based materials, ECC strain hardens after first cracking, similar to a ductile metal, and demonstrates a strain capacity 350 to 550 times greater than normal concrete. Even at large imposed deformation, crack widths of ECC remain small, less than 80 μm. With intrinsically tight crack width and high tensile ductility, ECC represents a new generation of high performance concrete (HPC) material that offers significant potential to naturally resolving the durability problem of reinforced concrete structures. In the past few decades, substitution of mineral admixtures, such as fly ash (FA) and Ground Blast-Furnace Slag (GBFS), has been of great interest and gradually applied to practical applications of ECC. It has been found that incorporating high amount of FA can reduce the matrix toughness and improve the robustness of ECC in terms of tensile ductility. Additionally, unhydrated FA particles with small particle size and smooth spherical shape serve as filler particles resulting in higher compactness of the fiber/matrix interface transition zone that leads to a higher frictional bonding. This aids in reducing the steady-state crack width beneficial for long-term durability of the structure. In this study, the workability, mechanical properties and durability of ECC different mixtures contains two mineral materials (slag / fly ash) as to replace part of the cement weight and two types aggregate (Silica/ River sand) were evaluated. The results showed that mixtures containing fly ash despite lower mechanical strength to compared with mixtures containing slag, significantly have higher performance in strain- hardening behavior at post- cracking portion. ECC mixtures performance against the durability testing (Rapid chloride penetration, Electrical Specific Resistivity, Drying Shrinkage and Accelerated Reinforcement Corrosion) were appropriate and quantitatively was to form of slag> fly ash. In this study, in order to calculate the direct tensile strength of ECC mixtures, a new model (different geometry) compared to other models (used by prior researchers) proposed and tested. The its results showed that the tensile strength measured by the new model compared to the previous models, was higher 10% to 17%.},
Keywords = {Engineered cementitious composites,mechanical properties,durability},
volume = {17},
Number = {5},
pages = {135-147},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6459-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6459-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {EbadiJamkhaneh, Mehdi and Davoodi, Mohammad Reza and EbadiJamkhaneh, Jav},
title = {Assessment of the ball joint behavior under combine loading},
abstract ={Space grids are highly modular structures assembled from components that are almost exclusively factory fabricated. The components therefore, are usually produced with high dimensional accuracy, with a high quality of surface finish and they are generally easily transportable, requiring little further work except assembly on site. Because of their modular nature, space grids may be extended without difficulty and even taken down and reassembled elsewhere. One of the most popular types of connectors that are widely used in the construction of double layer grids is the MERO system. The Mero KK space truss system, the first commercially available, is still considered to be one of the most elegant solutions for the construction of space grid structures. The elegance and simplicity of the Mero system means that it is not only used in buildings but also for shop displays and exhibition stands using lightweight materials. Circular tube members are connected to cast ‘ball’ joints at the nodes by a single concealed bolt for each tube. A double layer grid is combination of prefabricated tetrahedral, octahedral or skeleton pyramids or inverted pyramids having triangular, square or hexagonal basis with top and bottom members normally not lying in the same vertical plane. The connector is an extremely important part of a grid design. The type of connector depends primarily on the connecting technique, whether it is bolting, welding, or applying special mechanical connectors. It is also affected by the shape of the members. This system is multidirectional system allowing up to fourteen tubular members together at various angles. The system consists of tubular elements that are connected together by means of a MERO connector. The ball is located at the intersection of the longitudinal axes of tubular elements. The longitudinal axis of tabular element and all the constituent parts of its end connectors are along together. This axis is referred to as axis of member. The MERO system had only one type of standard joint, a sphere with 18 threaded holes and machined bearing surfaces at angles of 45, 60 and 90° to each other. A model of MERO connector is presented in this paper for double layer grid structure. The internal forces in the members of double layer grid are found using SAP software. These forces are applied as pressures on the MERO connector. The deflection and rotation patterns of the connector are studied under different loading conditions using the ABAQUS software. The forces to be applied on the connector are calculated using of displacementg control. In order to take into account the connector effects in structural analysis, their behavior under combined load should be predicted. In double-layer grids that are an important family of space structures, the main internal forces are axial forces. In the present study, to determine the force-displacement relationship of MERO jointing system, some tensile, compressive and bending simulation tests were carried out on a connector of this type using 3D finite element method. The obtained force-displacement and moment- rotation relationship were used under different load. The results of the finite element simulation with experimental results have a good match. It was also found that in both compressive and tensile loading, the ball came to the plastic stage. Compressive axial force increases the flexural stiffness of the connection and with increasing compressive force decreases the elastic bending moment.},
Keywords = {Mero Connection,Finite element,Moment-Rotation Relationship,Load-Displacement Relationship},
volume = {17},
Number = {5},
pages = {149-159},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12027-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12027-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Asakereh, Adel and ahang, masou},
title = {Numerical Analysis arching phenomenon at the core of the Baft Zoned embankment dam located in the Kerman},
abstract ={Today, large dams, including the type of soil or concrete offshore structures are the most important that in water supply needs of human societies play a major role. Dam stability in recent decades has been of particular interest to designers of earth dams. Soil arching in zoned embankment dams is a phenomenon where stresses are transferred from the softer core soils to the stiffer shell soils due to differential movements between the core and shell materials. In these structures, excessive stress transfer due to soil arching will lead to hydraulic fracturing occurrence in the low permeability core soils; which can cause significant internal seepage and erosion problems. This process is usually accompanied by internal erosion of soil particles, which leads to the formation of soil pipes or other erosion features that eventually cause failure of the dam. statistically shown that progressive piping and erosion are the primary contributing factor in 30% to 50% of earth dam failures. The easiest way to prevent hydraulic fracturing from occurring is to ensure that the total stresses along the upstream side of the clay core are always greater than the seepage-induced pore pressures. Thus, some authorities argue that making use of highly soft materials in core of dam which have not enough shear stress to suspend on shell materials is useful. Installation of instrumentation and monitoring during construction and initial operation will help to assess important parameters. Statistics show that the highest number of failures unstable dams, Respectively is related to earth dams, gravity, pebbles, multi-arc and arc. In this research, by modeling the Baft earth dam in finite element software PLAXIS and compare the results with the instrument results, confirmed the authenticity modeling and then, the arching phenomenon has been studied in the earth dam desired. Investigated parameters include the width of the core (core slide slope), the upstream filter layer thickness and compressibility foundation. The effect of the core side slope angle on soil arching between the clay core and the upstream shell was investigated by simulating three different core side slopes for a vertically oriented clay core: 1V:0.25H, 1V:0.33H and 1V:0.50H. To further investigate the impact of transition layer thickness, three different models with upstream filter thicknesses of 1, 3 and 6 m were analyzed. The effect of foundation compressibility on soil arching between the clay core and the upstream shell was investigated by simulating foundation rock having three different levels of compressibility. The elastic rock modulus values used in the current study were: 4×105, 8×105 and 12×105 kN/m2. that the effective parameters between these parameters to reduce of arching, is core slide slope that The core slide flatter ratio arching dramatically reduced. Then the thickness of the layer filter, which increases its thickness is reduced ratio arching. Thicker filter layers also have the additional advantage that, if they are designed properly, they can help prevent erosion of core materials into the downstream soils if a crack in the core does occur. The effect modulus of elasticity of the foundation had little influence and is negligible.},
Keywords = {PLAXIS,Arching,Zoned embankment dam,Instrumentation,PLAXIS},
volume = {17},
Number = {5},
pages = {161-168},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-11393-en.html},
eprint = {http://journals.modares.ac.ir/article-16-11393-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {GhodratiAmiri, G. and Rajabi, Elham},
title = {Sensitive index of damage in reinforcement concrete frames under seismic sequence using artificial neural networks},
abstract ={In seismic active zones, large mainshocks usually follow by numerous aftershocks. Because of the short time intervals between consecutive shocks, additional damage due to the accumulation of inelastic deformations from all sequences is increased and the structures that has been already damaged by the preceding shock collapse before any repair is possible. Moreover, despite the importance of seismic sequence phenomena on increased damage and the evidence of structural damage caused by the recent multiple earthquakes such as Nepal and Hindu-Kush (2015), most structures are designed according to the modern seismic codes which only apply a single earthquake on the structure in the analysis and design process. In this case, the structure may sustain damage in the event of the "Design earthquake", and this single seismic design philosophy does not take the effect of strong successive shocks on the accumulated damage of structures into account. For this reason, the effect of various parameters such as Peak Ground Acceleration, Magnitude, Shear Velocity Wave, Effective Peak Acceleration, Peak Ground Velocity, Epicentral distance, the time gap between first and second earthquakes, Period of reinforced concrete frames and etc, is examined on the damage of reinforced concrete frames under single and consecutive earthquakes. At first, six concrete moment resisting frames with 3, 5, 7, 10, 12 and 15 stories, are designed according to the Iranian Code of Practice for Seismic Resistant Design of Buildings (i.e. Standard No. 2800 guideline) and analyzed under three different databases with/without seismic sequences phenomena. For each database, single and consecutive earthquakes are selected according to Peak Ground Acceleration (PGA), Effective Peak Acceleration (EPA) and Peak Ground Velocity (PGV) criteria from Pacific Earthquake Engineering Research (PEER) and United States Geological Survey’s Earthquake Hazards (USGS) centers. At next step, in order to train the multilayer artificial neural networks with back-propagation learning algorithm, period of reinforced concrete fames (T) and some of earthquake features including PGA, PGV, EPA, magnitude (M), shear wave velocity in the station (Vs), epicentral distance (Epc) and time gap between consecutive earthquakes (Tg) as artificial neural network inputs and Park-Ang (1985) damage index - as the results of nonlinear dynamic analysis in OpenSees software and neural network target – are selected. For each database, 400 neural networks are designed with a different number of neurons in each hidden layer from 1 to 20 and ideal neural network is determined with the least value of Mean Square Error (MSE) and maximum value of regression (R) among all networks. Then, for considering the effect of input parameters on structural damage (Park – Ang 1985) caused by single and consecutive seismic scenario, the range and reference values for each group of input parameters – single and consecutive cases in each database – are chosen to be close to the median values and introduce to ideal neural networks and damage indexes are determined. The results show that structural damage caused by with/without seismic sequence scenario is more sensitive than other parameters to Magnitude and Acceleration for single earthquakes and the ratio of these parameters in the second shake to first for consecutive shocks.},
Keywords = {Artificial Neural Network,Damage Index,Seismic Sequence,Nonlinear Dynamic Analysis},
volume = {17},
Number = {5},
pages = {169-180},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-6604-en.html},
eprint = {http://journals.modares.ac.ir/article-16-6604-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Hosseinejad, Farideh and Kalateh, Farhou},
title = {Using Fuzzy FEM in Dynamic Coupled Analysis of Saturated Porous Media},
abstract ={In the present study, a fuzzy finite element model is developed to apply uncertainty of soil parameters on dynamic behavior of coupled saturated porous media. The interaction problem in the analysis of elastic soil matrix with Darcy pore fluid flow which is formulated by Biot is one of the complicated problems and its exact solution is so difficult, therefore it can be solved numerically. Finite Element Method is one of the numerical methods to approximate the dynamic solution of these problems and for convenient approximation of solution, model parameters need to be precisely known. On the other hand due to inhomogeneous and anisotropic structure of soil matrix, it is not possible to define the soil parameters with the crisp numbers. Consequently results that are obtained only one specific crisp value for an uncertain parameter cannot be representative for the whole spectrum of the possible results. To solve this limitation, application of fuzzy arithmetic proves to be a practical approach. For this purpose uncertainties in the soil parameters are taken in to account by the fuzzy numbers and shape function of input fuzzy numbers are derived from experimental data. In this study the coupled equations governing saturated porous media which are known as u-p equations, are solved by fuzzification of input parameters. For this purpose input parameters, the Poisson's ratio and modulus of elasticity, are treated as fuzzy numbers. To fuzzify a parameter, a certain number of degrees of membership are considered and by using fuzzy rules for each degree of membership a range of parameters are obtained which has lower and upper bound and the calculations are done for this upper and lower bounds. As a numerical example, problem of elastic soil column consist of two layers, loose and compacted sand, is analyzed. For solving this problem a finite element Fortran code has been developed and verified. For verification of developed Fortran code, the support of input fuzzy numbers was adopted in a way that the most likely amount of input parameters (m) be equal to the crisp input numbers that had been used by previous studies. The results indicated solution at α=1(probability of one hundred percent, which is the definite solution) is in good agreement with results of literatures. For other degrees of membership, the problem was solved with two constitutive D matrix for each α level to compute lower and upper bounds of output for that level. At the end, displacement and excess pore water pressure of sandy soil column which are produced under rapid loading are reported as fuzzy numbers. It means that it can be seen if Poisson's ratio and modulus of elasticity increase or decrease what will happen to displacement and excess pore water pressure. The results showed that coupling, change of input parameters of soil skeleton influence pore water pressure too. And as time increase this effect can be seen well. Also increase drainage distance causes a decreasing in the interaction between soil skeleton and pore water and this effect decreases by depth. Obtained result show that the number of fuzzy parameters (uncertain parameters) in equations increase the range of answers.},
Keywords = {finite element method,membership function,fuzzy number,coupled analysis},
volume = {17},
Number = {5},
pages = {193-206},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-4910-en.html},
eprint = {http://journals.modares.ac.ir/article-16-4910-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Mojezi, Mohsen and Biglari, Mahnoosh and Jafari, Mohmmad Kazem},
title = {Cyclic Parameters of High Plasticity Clay in Normally Consolidated Unsaturated Condition},
abstract ={Study of the seismic response of a site, requires the accurate estimation of the Shear modulus (G) and damping ratio (D) of under ground layers in that area. According to the unsaturated condition of an extensive part of the earth surface, it is necessary to perform unsaturated tests to determine dynamic or cyclic parameters of these regions. On the other hand, because of inherent complications of unsaturated testing equipment, this field of experience has had less attention. But in recent years by development of advanced experimental equipment some studies have been developed based on the dynamic parameters of unsaturated soils. A large amount of the researches related to cyclic and dynamic parameters of unsaturated soils are the studies about determination of these parameters in very small strain levels (initial shear modulus and initial damping ratio) and the effects of some factors such as suction, mean net stress, suction history, anisotropy and pre-consolidation on them, using bender element technique and resonant column torsional shear apparatus. But there is less attention in experimental studies in the strain ranges of medium to large and determination of the parameters G (shear modulus) and D (damping ratio), and also the normalized shear modulus reduction and damping ratio curves for unsaturated soils. In this research, it is tried to determine the shear modulus and damping ratio parameters in medium to large strain levels using suction controlled cyclic triaxial apparatus and study the effect of changes in matric suction and mean net stress on these parameters in a kind of unsaturated clay with plasticity index of 24 under high loading rates. In this regard, some tests are performed on different paths including two suction levels (zero and 300 KPa), in mean net stress level of 200 KPa and three deviatoric cyclic stress ranges (18, 42 and 81 KPa) up to 60 loading cycles. Also a comparison is done between the results obtained from the current research and the results of another research which was performed in the same paths on a fine grained soil with plasticity index of 12 using the same equipment. The results of this research show that increase in suction level results in raising shear modulus and decreasing in damping ratio values. In addition in the same strain level, by increasing the number of loading cycles, the shear modulus values are increased and the damping ratio values are decreased. Considering the results of current research (unsaturated cyclic tests on unsaturated normally consolidated fat clay with plasticity index of 24) with the results of another experimental research in the field of unsaturated cyclic tests on unsaturated normally consolidated lean clay with plasticity index of 12, in the same sample preparation process and the same stress paths, is indicated that the changes of the shear modulus values of the high plasticity samples are in the lower level related to the values of the samples with plasticity index of 12. In the other word, the increase in plasticity index decreases the stiffness of the samples considerably. But the change in damping ratio values is shown relatively the same trend in both groups of the samples.},
Keywords = {High plasticity clay,Shear modulus,Damping ratio,Unsaturated,Normally consolidated},
volume = {17},
Number = {5},
pages = {209-216},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-1763-en.html},
eprint = {http://journals.modares.ac.ir/article-16-1763-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Nasiri, Rahman and Maghsoudi, Ali Akbar and Maghsoudi, Mohamm},
title = {Evaluation of Engineering Properties of Control and Composite Concrete Consisting of Limestone Powder and Pozzolan},
abstract ={Portland-limestone cement (PLC) is a new, more sustainable version of portland cement that is becoming widely available in North America. Known as Type IL cement in the blended cement specifications of ASTM and AASHTO, it has already been approved by many transportation agencies and its use in structures and pavements is rapidly increasing. PLC implementation has been fueled mostly by interest in sustainability, but some experiences have also shown that it can be used to improve concrete performance and even mix economics. Beneficial performance synergies of PLC with fly ash and slag cement (SCMs) have been well documented. Recent research has also studied optimum PLC properties, the most beneficial types and characteristics of SCMs, and the extent to which SCM replacement rates can be extended. In addition to improved strength development, setting, and durability, this more sustainable PLC concrete has been found to improve finishing properties and the quality of formed or slipped surfaces. The webinar will review research and trial project data and highlight successful applications and project experiences to date, sharing implementation guidelines. More recently, the composite concretes which is consisting of Portland cement, lime stone powder and different types of pozzolans are used in a few countries. This type of concrete is more beneficial as a certain percentage of lime stone powder and pozzolan is substituted by cement weight in concrete. However, considering Iran, although considerable number of cement factories is available, and the economic cost of composite cement, the practical use of such cement is not yet seriously taking into consideration. When designing a concrete structure using composite cement, some of its characteristics and engineering properties become different from those of normal concrete, NC. These differences in material properties may have important consequences in terms of the structural behavior and design of composite concrete members. The design provisions contained in the building codes are, in reality, based on tests conducted on NC. The design of these structural members is not covered in existing codes of practice. Therefore for the aim of practical usage of composite cements, it is necessary to investigate seriously the plastic phase, engineering properties and durability considerations of this type of composite cement. In this paper, the chemical analysis of composite materials including cement, lime stone powder and Rafsenjan’s pozzolan are performed and the results and analysis of ten designed concrete mixes which are constructed and tested are discussed. The mixes are including control and nine composite (ie. cement type II of Kerman cement factory, Rafsenjan’s pozzolan and limestone powder) concrete. In plastic phase; the tests on slump, setting time and volume expansion of control and composite cement and in hardened phase; the tests on compressive strength for two wet (w) and %5 sulphate sodium (s) curing conditions, different type of tensile strength (i.e. splitting, European and flexural tensile strength) at short and long time ages and water capillary absorptions are carried out. Also, for concepts of practical use of such concretes in reinforced concrete structures, the compressive and tensile stress-strain diagrams are plotted by attaching sensors on two types of concrete. It was concluded that: i) the setting time of composite specimens were lower than that of control concrete specimen, ii) replacing of lime stone powder and pozzolan by cement weight caused to reduce the compressive strength of composite to that of control concrete at early and long ages however, ultimate compressive strain (εcu) of almost all the specimens reached 0.003 which is recommended by ACI standard. and iii) no considerable effect on the compressive strength of specimens was observed for two curing regimes of sulphate (s) and wet (w).},
Keywords = {Composite concrete,Pozzolan,Water capillary absorptions,Volume expansion,Engineering properties},
volume = {17},
Number = {5},
pages = {217-227},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-10145-en.html},
eprint = {http://journals.modares.ac.ir/article-16-10145-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Niroumand, Bahm},
title = {A field studies of comparison the bearing capacity of rammed aggregate piers and concrete piers under spread footing with variable the area replacement ratio.},
abstract ={This article compares the behavior of spread footing on rammed aggregate piers and spread footing on cast in place concrete piers as two types of semi-deep foundation with small-scale on-site. In this study, the area replacement ratio (pier on spread footing), composite (spread footing-pier) stiffness modulus and the bearing capacity of spread footing-pier are three main factors of the aim. For this purpose, 18 compressive load test in three groups with 6 elements composed of the following circular spread footings, spread footings on rammed aggregate piers, spread footings on concrete piers with constant diameter and length of piers and variable diameter of spread footing were built and tested in the coastal area of Bushehr port, Iran. In all three groups, the diameter of spread footings were 200, 250, 300, 350, 400 and 450 mm and in two groups of spread footings on piers, nominal diameter and length of concrete piers and rammed aggregate piers were 135 and 600 mm, respectively. The trial site was composed of a wet soil layer of low plasticity silt (ML). Underground conditions at the site were evaluated using in-situ and prevalent laboratory tests. Measurements performed in the site were composed of applied load and top settlement in spread footings on piers and pier's bottom settlement. The results show that, for the area replacement ratios (pier/spread footing) greater than 20%, the average of design limit stress and stiffness modulus of spread footings on concrete piers are 1.1 and 1.3 times of the corresponding values of spread footings on rammed aggregate piers, respectively. Also, for the area replacement ratios (pier/spread footing) less than 20%, the use of cast-in-placed concrete piers or rammed aggregate piers haven't any effect on the stiffness modulus and bearing capacity of spread footing on piers. In general, comparison of the results of load tests on spread footings on concrete piers and rammed aggregate piers and two types of piers shows that the performance of them is desirable in practice. Based on the results obtained in this study and previous research by the author in 2015 at the same site testing, the bearing capacity and stiffness modulus of concrete piers and spread footing on concrete piers are relatively greater than of rammed aggregate piers type. However, it is unclear in other local soil type, layering and other technical characteristics of such a result occur. On the other hand, as for the diameter and length of the trial piers, tip stress (against bulging) was governed on two types of piers and spread footing on piers. While, it is not clear with the occurrence of bulging deformation on the top of pier and effect of spread footing on it, such an outcome to be repeated. However, very little research has been done in this field, and as long as more research is done in this regard, for the decision to choose any one of these systems in action, case study should be done in this field. In this field, conducting a case study with a fewer loading tests and numerical modeling with validation of results can significant help to reduce the cost and duration of initial studies, prediction of results and to choose any of the systems.},
Keywords = {rammed aggregate piers,soil improvement,bearing capacity,stiffness modulus,the area replacement ratio},
volume = {17},
Number = {5},
pages = {229-240},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-5358-en.html},
eprint = {http://journals.modares.ac.ir/article-16-5358-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Shahbazi, A. and Niknam, M.S. and Amini, M.M.},
title = {Naphthalene removal from aqueous solutions using Graphene nanosheets: Optimal absorption studies and modeling},
abstract ={Polycyclic Aromatic Hydrocarbons such as naphthalene are dangerous for humans and the environment due to their carcinogenic and toxic properties. Thus, removing these pollutants from the environment is necessary. In this study, Graphene NanoSheets (GNS) was synthesised and applied for the removal of naphthalene from aqueous solution. The structure of nano-adsorbent studied using Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Optimal absorption studies for naphthalene removal from aqueous solution has been carried out at batch technique under various experimental conditions including adsorbent dosage (0.01 - 0.2 g/l), pH of solution (3 - 10) and initial concentration of naphthalene (3 – 15 mg/l). The isotherm of adsorption data was analyzed using Langmuir and Freundlich models and the kinetic of adsorption data modeled in optimum conditions using Pseudo-first-order, Pseudo-second-order, Elovich and Intra-particle diffusion models. The optimum condition has been achieved in the pH=10, initial concentration 13 mg/l and the adsorbent dosage 0.11 g/l and in these conditions, the removal percentage and absorption capacity of naphthalene was obtained 80.19% and 90.18 mg/g, respectively. The results indicated that adsorption isotherm and kinetic followed Freundlich isotherm (R2=0.97) and pseudo-second-order kinetic (R2=0.99) models, respectively. According to present study GNS can be used as an efficient adsorbent for the naphthalene removal from aqueous solutions.Polycyclic Aromatic Hydrocarbons such as naphthalene are dangerous for humans and the environment due to their carcinogenic and toxic properties. Thus, removing these pollutants from the environment is necessary. In this study, Graphene NanoSheets (GNS) was synthesised and applied for the removal of naphthalene from aqueous solution. The structure of nano-adsorbent studied using Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Optimal absorption studies for naphthalene removal from aqueous solution has been carried out at batch technique under various experimental conditions including adsorbent dosage (0.01 - 0.2 g/l), pH of solution (3 - 10) and initial concentration of naphthalene (3 – 15 mg/l). The isotherm of adsorption data was analyzed using Langmuir and Freundlich models and the kinetic of adsorption data modeled in optimum conditions using Pseudo-first-order, Pseudo-second-order, Elovich and Intra-particle diffusion models. The optimum condition has been achieved in the pH=10, initial concentration 13 mg/l and the adsorbent dosage 0.11 g/l and in these conditions, the removal percentage and absorption capacity of naphthalene was obtained 80.19% and 90.18 mg/g, respectively. The results indicated that adsorption isotherm and kinetic followed Freundlich isotherm (R2=0.97) and pseudo-second-order kinetic (R2=0.99) models, respectively. According to present study GNS can be used as an efficient adsorbent for the naphthalene removal from aqueous solutions.Polycyclic Aromatic Hydrocarbons such as naphthalene are dangerous for humans and the environment due to their carcinogenic and toxic properties. Thus, removing these pollutants from the environment is necessary. In this study, Graphene NanoSheets (GNS) was synthesised and applied for the removal of naphthalene from aqueous solution. The structure of nano-adsorbent studied using Fourier Transform Infrared (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Optimal absorption studies for naphthalene removal from aqueous solution has been carried out at batch technique under various experimental conditions including adsorbent dosage (0.01 - 0.2 g/l), pH of solution (3 - 10) and initial concentration of naphthalene (3 – 15 mg/l). The isotherm of adsorption data was analyzed using Langmuir and Freundlich models and the kinetic of adsorption data modeled in optimum conditions using Pseudo-first-order, Pseudo-second-order, Elovich and Intra-particle diffusion models. The optimum condition has been achieved in the pH=10, initial concentration 13 mg/l and the adsorbent dosage 0.11 g/l and in these conditions, the removal percentage and absorption capacity of naphthalene was obtained 80.19% and 90.18 mg/g, respectively. The results indicated that adsorption isotherm and kinetic followed Freundlich isotherm (R2=0.97) and pseudo-second-order kinetic (R2=0.99) models, respectively. According to present study GNS can be used as an efficient adsorbent for the naphthalene removal from aqueous solutions.},
Keywords = {Graphene NanoSheets,Polycyclic Aromatic Hydrocarbons,Optimal absorption,Isotherm,Kinetic},
volume = {17},
Number = {5},
pages = {241-251},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-2670-en.html},
eprint = {http://journals.modares.ac.ir/article-16-2670-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2017}
}
@article{
author = {Rostami, Vahid and AfsharFarnia, A.},
title = {The Evaluation of Footing Bearing Capacity Rest on Top of Retaining Wall Reinforced by Geogrid in Saturated and Dry Soil},
abstract ={Reinforced soil is a common technique to improve the soil properties and can be used in design of foundations and retaining earth structures. Reinforced earth structures are embankments which are reinforced with reinforcing elements such as geogrids, steel straps, etc. This study evaluates the strip footing bearing capacity that rest on near the geogrid reinforced retaining walls in saturated and dry sandy soil conditions. The previous researches have indeed studied the effects of many different parameters on the strip footing bearing capacity including the number of reinforcing elements, reinforcement depth, vertical distance of the reinforcing elements, etc. However, the retaining walls behavior in saturated embankment conditions has not so far been studied up to now so the emphasis in this article was to study the effect of saturation condition on the footing bearing capacity near the reinforced walls. For this purpose small scale laboratory model tests were carried out to investigate the behavior of strip footing bearing capacity that rest on near the geogrid reinforced retaining walls. A steel frame model box with inner dimensions of 0.5 m × 0.5 m in plan and 0.5 m in height was used. One side of the test box was made of Plexiglas for observations during the tests. The strip footing was made of a steel plate 0.49 m in length, 0.05 m in width and 0.02 m in thickness. An aluminum plate with thickness of 3mm used as retaining wall model. A two-way geogrid sheet with a tensile strength of 20KN/m was used to reinforce the sand bed. The sand bed prepared by sand raining technique and a water tank placed on top of the frame to saturate the bed and Overall, 90 tests were conducted. To evaluate the effect of geogrid length on strip footing bearing capacity in dry condition, three different lengths (L/B=3, 4, 5) was used. The bearing capacity of the strip footing increases with an increase in the geogrid length. Increasing of geogrids lengths prevents expansion of the failure area and allows for wide distribution of applied loads. Based on the BCR diagrams reveals that in most diagrams, the slope of the first part (i.e. L/B=3 to L/B=4) is larger than the slope of the second part, which indicates that an increase in the length to the L/B=4 level causes a significant change in the strip footing’s bearing capacity. As a result, larger increases do not have significant effects on the strip footing’s bearing capacity. Therefore, in this study, the L/B=4 length ratio was recommended as the optimum ratio considering economic problems. To study the effect of the geogrid depth on the footing bearing capacity in the saturated embankment, the bearing capacity at four different depth ratios of u/B=0.25, u/B=0.5, u/B=0.75, and u/B=1.0 are used and that compared with dry condition. The results are showed that increasing the geogrid depth introduced a descending trend in the bearing capacity of the strip footing, so that the full capacity of the geogrid sheet could not be utilized. One reason for this is that increasing geogrid depth would compress the soil between the footing and the geogrid, leading to large settlements. Considering the conditions of the present study, the depth ratio of u/B=0.25 selected as the optimum ratio.},
Keywords = {strip footing bearing capacity,saturated embankment,reinforced soil,geogrid.,},
volume = {17},
Number = {6},
pages = {1-15},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15806-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15806-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Ouhadi, v.r and Amiri, M.},
title = {Using Tailings of NanoClay Production Process in Environmental Geotectonic Projects to Retention Cu Contaminants},
abstract ={Soils contaminated with heavy metals are among the common environmental geotectonic problems all around the globe. Clay is considered as one of the best protective layers for environment to absorb polluters. Considerable SSA, very low permeability and the clays cationic capacity have been good factors to use these materials in geo-environmental projects vastly. It can react with the materials existing in the polluters because of the layered structure and special vast surface so the clay can absorb all or some of the dangerous polluter materials passing through the soil. Each part of the mineral materials constituting the clay, carbonate, organic materials, oxides, amorphous materials or remained phases can play a role in the process retention heavy metals. Carbonates play a special role in the process of the clay and metallic polluters’ interaction. The effect of the soil structure in retention heavy metal has been studied in many researches. In geotechnical environment view the clay mineral montmorillonite is one of the clays used in geo-environmental projects. Among the clay minerals montmorillonite has the highest property absorbing polluters. In the absence of clayey soils, compacted bentonite-enhanced sand mixtures are attracting greater attention as suitable material for contaminant barrier systems. The efficiency of these insulated barriers depends largely on their hydraulic and mechanical behavior. In landfills, as the main function of the liner is to minimize the movement of water out of the waste disposal facility, Landfill should satisfy three performance criteria if it is to perform satisfactorily as a barrier material. It should have low hydraulic conductivity (typically less than 1×10-9 m/s), should have sufficient strength in order to be stable during construction and operation, and it should not be susceptible to excessive shrinkage cracking due to water content changes that usually occur during the lifetime of the landfill. On the other hand, provision of the proper platform for landfills has been a concern of geotectonic and environmental geotectonic researchers in the past three decades. One of the objectives of this research was to introduce a material with suitable environmental geotectonic properties, minimum permeability, and maximum contaminant absorption potential. The process of producing nanoclay particles from bentonite clay with a top-down approach involves omission of some materials in the form of tailings. In related studies, the bentonite clay sample was divided into the following two main parts through physical and chemical processes: nano-montmorillonite (SLB) and process tailings (BLB). In this research, through a series of geotectonic and environmental geotectonic experiments the interaction of nano-montmorillonite interaction (SLB), process tailings (BLB), and bentonite clay samples with heavy metal contaminants was studied and analyzed experimentally. It shall be mentioned that the process of separating bentonite clay sample components was analyzed through microstructural X-ray diffraction (XRD) and specific surface area (SSA) experiments as well as scanning electron microscope (SEM) imaging. The tests conducted in the study were mostly on the basis of ASTM standard and the geo-environmental tests directions issued by McGill University of Canada. The soil carbonate percentage was defined by titration method. The specific surface area (SSA) was determined using the ethylene glycol-monoethyl ether (EGME) method. CEC was determined by the BaCl2 replacement method. The carbonate content of the soil was determined by titration, and the soil pH was measured in 1:10 soil solution.Also the soil pollution retention capacity was measured by titration test and HNO3 in different concentrations was added to the samples. Results of the present research suggest that process tailings (BLB) contain approximately 80% of copper as a heavy metal contaminant at a concentration of 100 cmol/kg-soil. In addition, permeability of the BLB sample and its inflation are approximately 5.2 10-10 m/sec and 70%, respectively.},
Keywords = {BLB,XRD,Heavy Metal,NanoClay,Landfill,.,},
volume = {17},
Number = {6},
pages = {17-28},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15452-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15452-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Bagheri, S. and Kabiri-Samani, A.R.},
title = {Hydraulic Characteristics of flow over the streamlined weirs},
abstract ={The present study is subjected to analytical, numerical, and experimental simulation of hydraulic characteristics of flow over the streamlined weirs. Numerical simulations were performed using an open source software namely OpenFoam. According to the objectives of the present study, to evaluate the results of numerical modeling, experimental investigation was conducted, studying different models of streamlined weirs, experimentally. The profiles of the experimental models as well as the simulated numerical models were designed based on the Joukowsky transform function. By analyzing the results of different turbulence models including standard k-ε model, realized k-ε model, RNG k-ε model, k-ω SST model and Reynolds stress LRR model, the k-ω SST model was chosen as the most accurate numerical turbulence model for the simulation of flow over the streamlined weirs. The results of the numerical simulations for different flow discharges and different geometrical characteristics, indicated that, increasing the flow discharge and the relative eccentricity in Joukowsky transform function, tends to increase the velocity and consequently decrease the pressure over the weir crest. Therefore, the lowest pressure and the most probable potential of cavitation belongs to the circular-crested weirs with λ = 1 and high flow discharges. Furthermore, the results show that the greatest bed shear stresses and the compressive forces occur at the downstream end of the circular-crested weirs, thus the downstream zone of the circular-crested weirs is responsible to large values of bed erosion. This is partly due to formation of shock waves, reduction of the flow depth and enhanced velocity of flow downstream of the circular-crested weirs. Furthermore, the lowest bed shear stresses occur at the upstream end of the circular-crested weirs. Therefore, potential of sedimentation upstream of the circular-crested weirs increases. Accordingly, by employing streamlined weirs with λ< 1, and an appropriate curvature, unfavorable flow conditions would be improved, leading to a more safe and economic hydraulic structure. The present study is subjected to analytical, numerical, and experimental simulation of hydraulic characteristics of flow over the streamlined weirs. Numerical simulations were performed using an open source software namely OpenFoam. According to the objectives of the present study, to evaluate the results of numerical modeling, experimental investigation was conducted, studying different models of streamlined weirs, experimentally. The profiles of the experimental models as well as the simulated numerical models were designed based on the Joukowsky transform function. By analyzing the results of different turbulence models including standard k-ε model, realized k-ε model, RNG k-ε model, k-ω SST model and Reynolds stress LRR model, the k-ω SST model was chosen as the most accurate numerical turbulence model for the simulation of flow over the streamlined weirs. The results of the numerical simulations for different flow discharges and different geometrical characteristics, indicated that, increasing the flow discharge and the relative eccentricity in Joukowsky transform function, tends to increase the velocity and consequently decrease the pressure over the weir crest. Therefore, the lowest pressure and the most probable potential of cavitation belongs to the circular-crested weirs with λ = 1 and high flow discharges. Furthermore, the results show that the greatest bed shear stresses and the compressive forces occur at the downstream end of the circular-crested weirs, thus the downstream zone of the circular-crested weirs is responsible to large values of bed erosion. This is partly due to formation of shock waves, reduction of the flow depth and enhanced velocity of flow downstream of the circular-crested weirs. Furthermore, the lowest bed shear stresses occur at the upstream end of the circular-crested weirs. Therefore, potential of sedimentation upstream of the circular-crested weirs increases. Accordingly, by employing streamlined weirs with λ< 1, and an appropriate curvature, unfavorable flow conditions would be improved, leading to a more safe and economic hydraulic structure.},
Keywords = {Streamlined weir,Joukowsky transform,OpenFoam software,Velocity profile,Pressure distribution.,},
volume = {17},
Number = {6},
pages = {29-42},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15811-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15811-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Bahaaddini, Mojtab},
title = {Size effect on the mechanical behavior of intact rock},
abstract ={Determination of the rock mass strength is a challenge for geotechnical engineers. Some part of this problem is related to complex interaction of rock mass components, intact rock and discontinuities, and the other part is related to difficulty in determination of the mechanical properties of intact rock and discontinuities. The common approach to determine the mechanical properties of rocks is undertaking laboratory experiments and extrapolate the insitu properties based on these laboratory experiments. This extrapolation, or in the other word size effect, has been remained as a challenge for practical rock engineers for decades. Size effect studies can be divided into two groups of one dimensional scale effect, in which the diameter of samples is fixed and the length of samples are changed, and three dimensional scale effect, in which the ratio of length to diameter, called slenderness ratio, is fixed and the diameter is changed. Review of previous studies on the effect of slenderness ratio on the strength of intact rock shows that in some studies as the slenderness increases up to specific value, the strength decreases while in other studies the slenderness ratio has no significant effect on the strength. Results of previous studies on the effect of sample diameter on the strength of intact rock are also inconclusive. Some studies show that as the diameter of sample increases, the strength decreases while other studies show the increase of strength up to specific diameter or no scale effect. This paper aims to study both one dimensional and three dimensional size effect on intact rock properties. To this end, around 120 sandstone samples with diameter between 19 to 145 mm and slenderness ratio of 1 to 4 were prepared and uniaxial compression tests were carried out on these samples. Uniaxial compression tests were carried out using MTS 815. Axial and circumferential extensometers were used to measure deformation of samples during experiments. Results of this study show that the increase of diameter up to 50 mm resulted in the increase of uniaxial compressive strength and no scale effect was observed for diameters greater than 50 mm. This trend was observed for all slenderness ratios. No scale effect was observed on the elastic modulus and the Poisson’s ratio. Therefore, the minimum diameter of around 50 mm, which is suggested by ISRM and ASTM standards, is the size that scale has no effect on the results of uniaxial compression tests. It was found that the increase of slenderness ratio up to 2.5 results in the decrease of strength and no significant effect was observed for greater slenderness ratios. To find out the reason of observed behavior, failure mechanisms of samples at different slenderness ratios were studied. Four types of failure mode were observed in the experiments; generation of a single shear plane, multiple shear planes, shear plane with some cracks in the center of specimens and tensile cracks parallel to the loading direction. It was found that at low slenderness ratios, samples are failed by propagation of tensile cracks which results in higher strength compared to the other failure modes. Therefore, the higher strength of samples with slenderness ratio of 1 is related to this failure mechanism.},
Keywords = {Scale effect,Slenderness ratio,Uniaxial compression test,Failure mechanism,Intact rock,},
volume = {17},
Number = {6},
pages = {44-55},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15808-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15808-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Beheshti-Aval, Seyed Bahram and Mohsenian, V. and Nikpour, N.},
title = {A Study on Seismic Performance of RC Tunnel-Form Building Structures With Irregular Plan},
abstract ={The tunnel-form falls under the category of industrial construction methods which is one of the modern construction methods for building houses. A current tendency in the building industry in many countries around the world with increasing city populations, is toward utilizing the modular construction system for development of multistory residential units. The tunnel-form system is an industrialized construction technique in which structural walls and slabs are cast in situ simultaneously using steel forms composed of vertical and horizontal panels set at right angles.The wall and slab frameworks consist of joining horizontal (table) and vertical parts that are reused on multiple stories of a building without being dismantled. The assembled sections are flown by crane from one story to the next. Once in position the gaps between the tables are filled with fillers. They vary in shape and size. The use of these systems can greatly reduce the time and manual labor involved in setting and striking the formwork. Their advantages are best utilized for mass building construction and also for simple designed structures. The main characteristic of a tunnel-form system are its relatively thinner components, i.e. walls and slabs compared to those of traditional reinforced concrete buildings.Through reduction of the construction time and proper performance during the past earthquakes, this type of building construction is recognized as a suitable method used in mass production projects. Despite its widespread use and different behavior in respect of other systems, in the current building design codes, this system has not been considered as an independent structural system. Unfortunately no special seismic code is published for reinforced concrete wall-slab system with tunnel-form and there is only little information about the seismic behavior of this structural system type in technical and research docs. Therefore based on reasonable numerical results, seismic behavior and performance of structures constructed with this technique considering the effective factors on response is highly noteworthy in a seismic code development process. Due to domination of the natural torsion mode respecting to the natural transverse mode based on eigen value analysis of their structural model, use of this system with an irregular plan by the authority building standards departments like the Building and Housing Research Center of Iran has been declared illegal. However, so far no information on their seismic behaviors and vulnerability reports subjected to past earthquakes are available. Necessitating regularity of tunnel-form constructions in the plan and elevation, despite superior advantages such as high-speed manufacturing process and high quality assurance, several limitations in terms of architectural design requirements are one of the basic problems of using this structural system in urban zones. In this paper, the seismic behavior of the two-tunnel-form structures of 5 and 10 stories with an irregular floor plan which were designed based on current building codes in range of nonlinear behavior, is studied. Indeed, performance levels under the design earthquake using the response history and pushover analysis are specified through excitation in two longitudinal and traversal plan directions simultaneously. The results showed the appropriate seismic performance despite the irregularities. Both structures subjected to the design earthquake are placed in the immediate occupancy performance level. It seems that the provision no. 5 of the regulations issued by the Building and Housing Research Center of Iran pertaining to tunnel form building design and construction that stipulate regularity requirement of the tunnel-form plan , at least, are strict and scrupulous for the studied structures.},
Keywords = {RC tunnel form system,plan irregularity,seismic performance levels,design code,},
volume = {17},
Number = {6},
pages = {57-68},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14741-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14741-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Biglari, Mahnoosh and Ashayeri, Iman and Hoshyar, Yadegar},
title = {Evaluating inversion of microtremor H/V spectrum in extracting shear wave velocity profile with Down-Hole test results},
abstract ={The velocity of shear wave, which is utilized in evaluation of the stiffness and strength of subsurface layers, the geotechnical site effects of earthquakes, and determination of the profile of subsurface layers is one of the most prominent and essential parameters in geotechnical studies. The profile of shear wave velocity of soil layer is usually discerned in the site by means of prevalent direct seismic and geophysical methods such as reflection, refraction like SASW and MASW, and borehole ways or indirectly, by geotechnical methods such as conducting CPT or SPT sounding and employing experimental relations among Vs and CPT or SPT quantities. As far as these methods need to dig boreholes, it is obvious that deploying borehole geophysical methods or geotechnical ones to certify the profile of shear wave velocity is expensive and time-consuming. As an economical and practical alternative, the measurements of microtremors which can be easily implemented on the ground surface at a single station. Firstly, the method registers ambient vibrations; then, the spectral proportion of the average of horizontal components to vertical component of microtremors (H/V) are determined. At the end, shear wave velocity profile of the site are discerned by inversion of the H/V spectrum in a reversal algorithm. The analyses are easily performed by means Dinver program of useful package of Geopsy software. In this study, single station microtremor measurements are done at six points along Kermanshah Urban Railroad project. In order to determine shear wave velocity profile from inversion of H/V spectrum, four shear wave models with 3,5,7,and 10 layers are initially suggested for all mentioned six points. All initial models were similar in parameters like thickness of layers and range of shear wave velocity in each layer, so that final conclusions and interpretations can be made for future studies. The best of achieved shear wave velocity profiles in terms of minimum misfit error of inversion of horizontal to vertical spectral peak are compared with the result of field Vs measurements that were performed by down-hole experiments. The most outstanding point is that, the procedure is utilized to find shear wave velocity profile without considering the results of down-hole tests for thickness and velocity limits. The comparison showed that there are significant compatibility between shear wave velocity profiles achieved by inversion method and the results of field down-hole tests. Generally, this compatibility increases with increasing the number of layers from three to ten layers of initial models. Furthermore, the depth of exploration grows with increasing the number of layers as well as the accuracy of profiles, so the initial model with 10 layers has more consistency with the results of borehole experiments of all six points in relation to other models. However, it is obvious that the time for analyzing initial model with 10 layers is more than other ones and a tradeoff between accuracy and time of analyses must determine the acceptable results. In conclusion, inversion of H/V spectrum method shows the ability to appropriately estimate shear wave velocity profile even in deeper sediments in relation to down-hole tests.},
Keywords = {Shear wave velocity profile,single station seismogram,microtremors,inversion of horizontal to vertical spectrum ratio,},
volume = {17},
Number = {6},
pages = {69-79},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15809-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15809-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Taghipoor, Mohammad and Kavussi, Amir and Kazemian, Farbod and adresi, mostaf},
title = {Evaluation of brick powder to improve the fatigue behavior of asphalt mixtures.},
abstract ={Acting as a surface which is supposed to tolerate several reloading of heavy axes, pavement shall hold enough resistance against failures. Fatigue phenomenon is one of the most important causes of weakness in road pavement, which is occurred due to reloading of it. Many laboratory researches are carried out with the purpose to enhance fatigue life of asphalt concrete mix, in which researchers have tried to improve quality of asphalt concrete mix against load carrying transportation vehicles. During recent years, additives like polymer, iron powder, hydrated lime, glass wastages, crumb rubber and brick powder are also considered for improving tar and, consequently, asphalt mix properties. Generally, hot-mix asphalt (HMA) mixtures consist of three components: mineral aggregates, asphalt binder and air voids. It is well recognized that mineral fillers play an important role in the properties of mastics and hot-mix asphalt (HMA) mixtures. Better understanding of the effects of fillers on the properties of mastics and HMA mixtures is crucial to good mix design and high performance of HMA mixtures. In this stydy, the effect of brick powder on fatigue parametrs have been investigatedFiller content for mix design should be determined based on the overall performance of HMA mixtures.It has been recognised with growing concern that agricultural and industrial wastes are increasingly produced in large volume. In order to reduce environmental hazards and conserve natural resources, the use of waste materials in highway pavements would be extremely effective in terms of recycling waste materials. The main purpose of this study was to investigate the effects of waste materials as filler on the performance of hot mix asphalt (HMA) mixtures.It is well recognized that mineral fillers play an important role in the properties of mastics and hot-mix asphalt (HMA) mixtures. Better understanding of the effects of fillers on the properties of mastics and HMA mixtures is crucial to good mix design and high performance of HMA mixtures. Laboratory experiments were conducted to investigate the effect of different fillers on properties of mastics and HMA mixtures. The properties of HMA mixtures were investigated by Marshall, indirect tensile stiffness modulus and indirect tensile fatigue tests. The results indicated that WBP mixtures exhibited higher fatigue life and better performance than control mixtures. With the increase of filler content, some properties of HMA improved while others decreased. The effects of filler were exerted on HMA mixtures through the mastic. Fillers with rough particle texture (such as manufactured sand) tend to increase the stiffening effect of the mastics and mixtures. Considering the overall effects of filler on the properties of HMA mixtures, a filler content range would be required in order to ensure the performance of the mixtures. Waste materials can be mainly regarded as the following classifications: (a) industrial wastes such as cellulose waste, slag, bottom ash and fly ash; (b) municipal/household wastes such as incinerator residue, scrap rubber and waste glass; (c) mining wastes such as coalmine refuse and (d) construction and demolition Based on the results, in consequence of increased awareness of environmental issues and natural resources constraints, the studied waste materials can be advantageously utilised in road construction.},
Keywords = {Pavement,Asphalt mixtures,Additive,Brick powder .,},
volume = {17},
Number = {6},
pages = {81-91},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14345-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14345-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {SoltaniMohammadi, Masoud and Jafari, Mohamm},
title = {The investigation of pushover lateral force profile characteristics considering record uncertainties},
abstract ={Abstract: In recent years nonlinear static analysis method has been widely used in the field of performance based earthquake engineering. Whereas the capabilities of this method is well recognized, it still has inherent shortcomings. Accordingly, by considering aspects such as nonlinear properties of members, higher modes effect, and the computational cost, the accuracy of the method should be investigated. Although an enormous study have been carried out to improve the pushover analysis, the proposed methods are almost deterministic and cannot directly consider the seismic records uncertainties. Toward this challenge, the present study aims to examine the requirements of inelastic static analysis method through a comparison with incremental dynamic analysis results. The general purpose of the pushover method is to yield the maximum story responses (shear and drift) expected during the earthquake. For this reason, the selection of the dynamic response absolute maxima is discussed and different criteria are investigated; maximum displacement versus corresponding base shear, maximum displacement versus maximum base shear and, finally, maximum base shear versus corresponding displacement. Therefore, using the information obtained from dynamic analysis, the characteristic of the proper lateral forces that can represent the average of the maximum effect of the ensemble of earthquake records and consider the inherent records uncertainties, can be obtained. So, to derive the characteristics of equivalent lateral forces based on the dynamic response of the system, four different lateral force profiles can be considered; (1) F1: lateral forces create the same average story forces as dynamic analysis, (2) F2: the profile and intensity of the lateral forces that produce the average of the maximum story shear induced by seismic record ensemble, (3) D1: the lateral force profile is chosen in a way that it can produce the same maximum story drifts as dynamic analysis, and (4) D2: the forces that their responses best represent the average of the story lateral displacement in dynamic analysis. The comparisons are performed for three levels of the typical small, medium and high-rise buildings denoted as four, twelve and twenty-story shear frames. The mathematical model of the frames are chosen as the smoothly varying diﬀerential Bouc–Wen model. Because of the versatility and mathematical tractability of the Bouc-Wen model, by altering diﬀerent parameters of the model, it can simulate various structural behavior with any degree of nonlinearity. The estimated responses are compared to those resulted from the nonlinear dynamic analysis. The comparison procedure in the validation process is conducted in two levels; structural global level results (base shear and roof displacement) and story level results (the story drift and lateral force profiles). Furthermore, using the considered characteristics of the lateral load profile, the probabilistic capacity curve which has the potential to be used for assessing different parts of the structure for different performance levels is extracted. As we expect from static nonlinear analysis the demand of the stories should reach their maximum. In fact, in the low-rise structure when the roof displacement reach its maximum, all of the stories also lean towards their maximum demands. By increasing the structures height (followed with higher modes effect), the result of classic pushover analysis cannot correctly estimate the demands and it differs from the result of dynamic analysis.},
Keywords = {Bouc-Wen model,stochastic linearization,probabilistic capacity curve,extreme value,},
volume = {17},
Number = {6},
pages = {93-107},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14639-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14639-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Habibi, A.R. and jami, E.},
title = {},
abstract ={},
Keywords = {},
volume = {17},
Number = {6},
pages = {109-119},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-33442-en.html},
eprint = {http://journals.modares.ac.ir/article-16-33442-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Heidari, T. and ShahniKaramzadeh, N. and Ahadiyan, J.},
title = {Analysis of Flow Front Characteristics of Convergent and inclined Plane Surface Jet in Stagnant Water Resources},
abstract ={This study presented the results of an experimental study on the dense flow discharging from convergent and inclined plane surface jet in stagnant and deep ambient resources. Development of industrial and commercial activities throughout the world leads to pollution of water resources. For example, The salt water obtaining from desalination process whose density exceeds the one of the ambient water is discharged into the sea by the desalination plants through discharging structures. Therefore, it is essential to study related processes to suitable transfer of effluent into the ambient. With respect to the importance of this matter, extensive studies have been conducted in recent years as physical and numerical modeling on examining and understanding of flow behavior discharging through submerged and surface jets. This study discusses the plunge and impact location under the effect of different variables. The study tests were carried out in a 3.2×0.6×0.9 m3 flume. The Jet fluid obtained from salt dissolution in water was prepared in three concentrations of 5, 15, and 45 g/lit. To show fluid’s moving path, the obtained solution was colored by using a substance with no effect on density changing. The flow rate of the jet fluid in values of 0.042, 0.08 and 0.105 lit/sec was adjusted by using an electromagnetic flow meter with the accuracy of 0.01 lit/sec. The injection of the jet fluid was carried out by using rectangular channels in four convergence angle of 12.5, 25, 45 and 90 degrees and the constant width of 0.06m. Width of the outlet section in all the channels were considered 0.035 m. Discharge channels injected the jet fluid tangent to the surface of the ambient water. Thus, the channels were installed and adjusted on a base at slopes of zero, 0.04 and 0.08 and certain convergence angle. The water depth in the flume was adjusted at a constant value of 0.7m in all experiments. The ambient fluid was settled before injection of the jet fluid. During this time interval, the temperature of the jet fluid and the ambient fluid were measured by a thermometer and their densities were measured by a hydrometer. For each experiment, the moving path of the jet fluid in the receiving ambient was recorded by using a Sony digital camcorder (DSC-WX220) with the frequency of 50 FPS. This camera recorded the images of flow’s section that was placed in front of the flume’s wall and perpendicular to the central vertical plane of the jet flow. The data was obtained by using of images routing process. Based on the results, the 8-percent slope has the longest length of plunge and impact locations. The 8-percent slope provides high initial momentum. Therefore, the flow has further advance in this condition. Slopes of 0 and 4 percent are very close to each other. Although the value of initial momentum exceeds zero in the 4-percent slope, the length of plunge and impact locations in the 4-percent slope are lower than zero slope. The initial momentum is divided into X and Z directions in 4 percent slope, but all initial momentum is in X direction in zero slope. While the longitudinal slope of the discharge channel is fixed, the length of plunge and impact locations reduce with the jet fluid concentration increasing. Density difference and buoyancy force increase with the concentration increasing. Flow becomes denser and it loses its contact with the surface more quickly. Besides that, the length of plunge and impact locations increases with the convergence angle decreasing. The initial momentum and the discharge velocity of jet flow increase with the convergence angle of discharge channel decreasing. Increasing the initial momentum leads to further advance of jet flow. As the ambient has a fixed depth, was seen the location of the plunge point in the range of 1.2 and the location of the impact point depending on the ambient depth. Finally, the ratio of the length of plunge to impact locations for data was within the range of 0.1-0.8.},
Keywords = {Surface jet,Dense jet,Convergence,Plunge location,Impact location,},
volume = {17},
Number = {6},
pages = {121-129},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14616-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14616-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Khosravi, Mahdi and GhoreishiNajafabadi, Sayed Hossein and Khosravi, Mohammad Hossei},
title = {Development and Investigation of a Simultaneous Dewatering – Excavation Method for Reducing the Settlement in the Vicinity of Construction Pit},
abstract ={Steady population growth resulted in increasing the land prices which lead to construction of deep excavation. Therefore the use of underground spaces is economically acceptable. One of the most important issues in the design of underground spaces and deep foundation pits is the existence of groundwater and how to control it. The influence of groundwater on a structural project can be very extensive and it may affect the structural design, performance and the total cost of the project significantly. Many problems related to ground water have been observed in excavation sites recently. Those problems have made significant delays in construction process and sometimes lead to significant re-design of the entire operation process. Considering the negative influence of groundwater on the reinforcement system, (e.g. nailing and anchoring) as well as the difficulty of excavation process under wet condition, water must be pumped out from the excavation area. The process of ground water discharge from the construction area which results in lowering the ground water level in that area is called dewatering. Dewatering operation may lead to ground settlement in the vicinity of construction pit which may damage the building. Although the damage due to ground settlement may be negligible, the potential consequences, especially in connection with claims of third parties, requires sufficient attention. In recent years, dewatering and lowering groundwater levels along deep foundation pits subway tunnels in urban environments caused some significant ground subsidence. The mechanism of this type of ground subsidence is that due to water drainage from the soil layers, the hydraulic pressure decreases leading to an increase in the density of the soil and therefore, ground settlement. Dewatering can leads to ground subsidence in different ways where some of them are as: a) removing the finer soil particles from the ground during water pumpage due to a poor pumping performance, b) in the case of dewatering by pumping water from the floor of excavation pit, piping and boiling can reduce the soil strength properties, leading to a failure in the soil mass and c) compaction of the compressible soils or crushable sandy soils due to increasing the effective stress. Some methods such as cut off walls and artificial injection can be used to reduce the ground settlement due to dewatering, but these methods are very time consuming and costly. Furthermore, methods such as artificial injection may have low efficiency and cause environmental effects. Therefore providing a new technique for reducing the dewatering induced ground settlement in less time and cost is necessary. The strategy proposed in this study is to apply a step by step dewatering method, by setting pumping from drainage wells, coincides with the excavation process. For this purpose the PLAXIS2D software is employed as a finite element method to model the settlement due to dewatering. This operation could be applied by modeling two deep foundation pits with the same structures and different groundwater conditions. The proposed step by step method was modeled in this software by estimating the excavation time and coinciding it with water pumping. Step by step dewatering method has some advantages such as reducing the amount of settlement behind the wall and asymmetric ground settlement under adjacent foundation, reducing the amount of water pumping out of the ground, decreasing the Mohr-Coulomb full plastic points in the range of geogrids and reducing the time and cost of dewatering.},
Keywords = {PLAXIS2D,Groundwater,Excavation,Dewatering,Ground settlement,},
volume = {17},
Number = {6},
pages = {131-143},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14481-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14481-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Roushangar, Kiyoumars and Ghasempour, Roghayeh},
title = {Modeling bed-load discharge in sewer pipes with different boundary conditions using Gene Expression Programming (GEP)},
abstract ={Accurate prediction of the sediment load is one of the important issues to water engineering. Due to complexity of sedimentation phenomenon and influence of various parameters on estimation of sediment transport rate, determining the governing equations are difficult, and classical mathematical models are not sufficiently accurate in this regard. In the present study the applicability of Gene-Expression Programming (GEP) for modeling bed load discharge in sewer pipes with different boundary conditions was assessed (i.e. fixed and movable beds). Therefore different input models based on theoretical concepts were defined for each boundary condition. In order to develop the models, under two scenarios, different input combinations were considered, first scenario (Scenario1) which uses only hydraulic characteristics and second scenario (Scenario2) which uses both hydraulic and sediment characteristics as inputs for modeling bedload discharge. The sewer pipes experimental data available in the literature were applied for training and testing the employed GEP. For evaluating the efficiency of the models three statistical indexes which called: Determination Coefficient (DC), Correlation Coefficient (R) and Root Mean Square Errors (RSME) were used. Then the accuracy and capability of several available bed load formulas such as Ackers, Neilsen, May, Mayerle and Laursen were investigated and compared with GEP- best modes in each boundary. Also with considering this point that may there is no information about bed boundary condition and for evaluating the applicability of applied technique for a wide range of data; all data series of sediment transport were combined. Then, for predicting Cv, as the dependent variable, several models of Scenarioa 2 analyzed for the combined data. The obtained results confirmed the efficiency of Gene-Expression Programming method for estimation sediment discharge in sewage pipes, and proved this method superior to the semi- theoretical relationships. According to the results it was found that in scenario 1, for all of the cases, model (IV) with input parameters of Fr and y0/D presented better performance than the others models, however it was observed that Scenario 2, which took advantage of both hydraulic and sediment parameters as inputs for modeling sediment discharge in sewer pipes performed more successful than Scenario1 which used only combinations of hydraulic parameters as input variables for models. Comparison between the results of separate data sets and combined data set revealed that analyzing data sets separately led to more accurate outcome. According to the results from fixed beds, it was found that adding Frm and d50/y as an input parameter increased the accuracy of the models. For both smooth and rough beds, the model with input parameters λs, Frm, Dgr, d50/y presented better results from the RMSE, R, and DC viewpoints (i.e. highest R and DC and lowest RMSE). For movable beds condition in the two cases of separate dunes and continuous loos bedform, the model with input parameters of ys/D, Frm, Wb/y0 showed more accuracy. This model showed the influence of flow depth and width and depth of movable bed in estimating of bedload transport in sewer pipes. For loose beds Frm has dominant role than other parameters.},
Keywords = {Sediment,Gene Expression Programming (GEP),Sewer pipes,fixed and movable bed.,},
volume = {17},
Number = {6},
pages = {145-157},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15807-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15807-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Ghasemzadehmosavinejad, s. Hosein and Shadmani, Ali and Tahmouresi, Behz},
title = {Mechanism of SBR latex effect on mechanical strength, permeability and microstructure of concrete containing asphalt waste},
abstract ={The use of recycled materials in Portland cement concrete (PCC) has become more and more popular in recent years. Most recycled materials applied in PCC are used to replace coarse aggregates, fine aggregate, or act as cementitious additives. When using recycled materials in PCC, it is desirable that the properties of the concrete can also be improved. Plain PCC, while typically having high strength, generally possesses very low post failure toughness, which may cause abrupt failure of structures and short pavement life. Reclaimed or recycled asphalt pavements (RAP) have been routinely used in the construction of pavement granular bases and hot-mix asphalt concrete. RAP is the removed and/or processed asphalt pavement materials containing both aged asphalt and aggregates. The asphalt coated on the surface of the aggregates typically forms a film with a thickness between six to nine microns. The use of RAP in PCC, though seems to be a viable solution to improve the toughness, has received little attention by research communities. Cementitious systems incorporating polymers have received considerable inter- national attention, especially over the last 30 years or so. The reason for this interest can be attributed to the improved engineering properties when compared to the unmodified materials, e.g. tensile/flexural strength, toughness and durability, the latter including resistance to carbonation, chloride penetration, and frost damage. Additionally, these systems may be used as repair materials where a good bond with the existing concrete or steel is required. Many polymer concrete combinations are available. Polymer-modified cement mortar and concrete (PMC): polymer particles in the form of a latex or redispersible powder are added to a fresh cementitious mix which is then cured. The most commonly used latexes are aqueous suspensions of styrene- butadiene-rubber (SBR) and various acrylics (Ac) containing 45±50% polymer solids. In SBR, the ratio of styrene to butadiene governs the properties of the polymer, with 60±65% styrene giving a good balance. Higher styrene contents would improve compressive and tensile strengths but reduce adhesion and raise the minimum film-forming temperature (MFT). In this study, the effect of SBR latex and silica fume on the mechanical strength (compressive, bending, and splitting tensile strength, elasticity modulus, toughness index), permeability (water penetration, rapid chloride penetration (RCPT), electrical specific resistivity) and microstructure of concrete made with recycled asphaltic aggregates to replaced with natural coarse aggregate (33%, 66% and 100% by weight) were studied. Results showed that the adding of latex and silica fume significantly increased mechanical strength and decrease permeability of concrete mixes. quality and microstructure of interfacial transition zone (ITZ) between aggregate- cementitious matrix by use of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analysis (EDX) was evaluated. SEM images showed that the mixtures containing latex and silica fume had uniform and smooth structure at surface aggregate- cementitious matrix, and also EDX analysis represents reducing the thickness of ITZ and the calcium to silicon ratio. For assessment of latex effect mechanism on compressive strength, three different type of curing on cube mixtures were applied. The results showed that compressive strength of specimens cured at temperatures significantly increased, which indicates of heating- help to formation polymeric membrane in specimens containing latex.},
Keywords = {Mechanical strength,Microstructure,Permeability,SBR latex,Recycled asphaltic concrete,},
volume = {17},
Number = {6},
pages = {159-170},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-20186-en.html},
eprint = {http://journals.modares.ac.ir/article-16-20186-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {KasehgarMohammadi, Shoaib and Eghbali, Porya and KasehgarMohammadi, Abozar},
title = {The examination of mixing time on the compressive strength of Nano-silica concrete with rice husk pozzolan},
abstract ={Due to the increasing use of concrete and the use of additives in it , research in this direction is very important . Resistance is one of the effective values in the design and control of concrete quality that numerous factors and parameters affect it . Perhaps increasing in concrete mixing time is one of the parameters that are considered less attention and in this research ; the effect of mixing time on compressive strength of Nano - silica concrete with pozzolan rice husk was studied and were compared with concrete without Nano - silica and pozzolan rice husk .Therefore the effect of sulfate to reduce the resistance of this type of concrete was studied and compared . So , a number of pieces of concrete cube with sides of 15 cm contains %1 Nano - silica and 20% pozzolan husk Rice with a time of mixing varies between 10 to 40 minutes , that every 5 minutes , 3 samples of concrete were taken and made in the days 3 , 7 and 28 under the stress test and ultimately the results of mixing different compressive strength by the time was drawn and reported . Rice husk also tested and its components determined and compared with the standard . Nano - silica concrete and concrete pozzolan rice husk and without Nano – silica and pozzolan was also photographed to compare the density of particles , and at the end testing plan was written by Taguchi testing of concrete . The results show that for the most compressive strength of concrete pozzolan Nano comes with rice husk , the right time (optimal) 25 minutes with a Taguchi test results differ by about 9 percent lower than the margin of error is permitted , that at this time the concrete maximum compressive strength shows the maximum compressive strength at 28 days after the concrete 415 kg/cm2 and then does not show significant strength concrete . Pozzolan concrete without silica and rice husk increasing mixing time increases the compressive strength of concrete 375 kg/cm2 in 28 days from the time the concrete mixing process increase the resistance of shows . Ash consumption in the non - crystalline silica , which is 88% of the project , has shown its high pozzolanic activity . Physical and chemical (XRF) examination showed that rice husk ash used in this project within the requirements of ASTM C-618 for pozzolan is located . XRD results show that the consumer is fully amorphous silica from rice husk ash . As the electro - microscopic pictures (sem) is observed in samples without Nano - silica and pozzolan rice husk , the concrete has uneven texture and large crystals are clearly visible which are connected with needle - shaped crystals and large pores are clear in concrete . However , the concrete samples with Nano - silica and rice husk pozzolan , concrete has a more amorphous structure which are homogeneous and integrated together . And the porosity of the concrete is significantly reduced , which increases the resistance of concrete.},
Keywords = {Nano-silica,rice hull pozzolan,mixing time,the compressive strength of concrete,Taguchi experimental design,},
volume = {17},
Number = {6},
pages = {171-181},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14420-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14420-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {mohammadaliha, mohammadreza and Behbahani, hamed and fattahiamirdehi, hamidrez},
title = {Statistical analysis of mode I fracture mechanics of asphalt mixtures at low temperature based on Weibull prediction model},
abstract ={This paper describes an evaluation of low temperature cracking of asphalt pavement and its propagation agents. Low temperature cracking is one of the noticeable deterioration of asphalt pavement in cold climate regions. This work employed a repeatable semi circular bending (SCB) fracture test to evaluate the low temperature fracture resistance of asphalt mixtures, additionally a large number of edge cracked semi circular bend specimens containing 4% and 7% air voids are used and subjected to symmetric three-point bending load at -10 °c to measure fracture toughness. The effect of air voids on pure mode I asphalt fracture are investigated experimentally and Linear Elastic Fracture Mechanics, its assumptions and effective crack tip parameters introduced, which is used in asphalt fracture mechanics. Then fracture toughness as a main parameter of fracture in the asphalt mixtures is calculated and various methods with different specimen types for determining the fracture toughness of asphalt has been viewed and Asshto suggested method has been discussed, which applied to the experimental part of this work. According to the statistical principle, the experimental results were analyzed by Weibull statistical distribution model in order to present the prediction models for each asphalt mixture with different air voids. The two-parameter and the three-parameter Weibull distribution function was applied to air voids data, Thus compared these two functions. Within the statistical analysis, the probability function for brittle fracture suggested by Wallin using a Weibull analysis that have the three parameters, Kmin, m and K0 ,all of which predicted in this study. The analysis of the results also revealed that Weibull distribution model is one of the most appropriate function for disscussing the volumetric properties of asphalt mixtures.Furthermore, a statistical analysis illustrated that Weibull model is also able to predict the statistical parameters for each set of test data, By preliminary data from the tests and also a well- defined Transfer Coefficient from the previous experimental data that the other researchers obtained through their studies, can be predicted the three-parameter and the two-parameter of Weibull statistical model such as Kmin and K0 which have significant role for asphalt fracture mechanics. In addition to the parameters of Weibull distribution, the average fracture toughness or the average stress intensify factor for asphalt specimens can be predicted from this type of the statistical analysis. In conclusion, this paper emphasises on the statistical and the experimental aspect of asphalt fracture mechanics that has investigated Weibull distribution model and the ability of this model to predict the important fracture parameters and the average stress intensify factor from a determined experimental data based on volumetric properties such as air voids. Finally, by investigating the errors for different models that suggested in this paper, indicatin the suitability of this model to predict the actual values of asphalt fracture.},
Keywords = {Mode I Fracture of asphalt,Weibull model,Low temperature Cracking,},
volume = {17},
Number = {6},
pages = {183-193},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14939-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14939-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {mohamadi, Mahdieh and Barghian, Majid and Mostofinejad, D},
title = {Alkali effect on the bond-strength of FRP-concrete bond in EBR and EBROG methods},
abstract ={Various researches have been performed regarding the deterioration and behavior of fabrics made from carbon, glass and aramid in different environmental conditions. Carbon fibers reinforced polymer (FRP) are very corrosion resistant. The CFRP laminates are extremely useful in very corrosive atmospheres, such as marine and aggressive chemical atmospheres. They have been advanced over the years because of their high strength, light weight, long-term durability and high resistance to deterioration. The very thin (0.2 - 0.4 mm) laminates are very easy to apply and can be applied in cross directions without any difficulty. Environmental conditions impact on the bond strength of FRP-to-concrete has sparsely been investigated. The sources of CFRP bond deterioration can originate from alkaline attack and thermal expansion. Alkaline attack occurs at the interface of the concrete and a CFRP laminates with the resulting damage to the matrix of the CFRP laminates. Also, alkali aggregate reaction can lead to the destruction of concrete elements. However, studies in this field are not enough and for externally bonded FRP materials, no such long term test results are available yet. Severe corrosion damage can often be prevented by a correct treatment of the structure against chemical influences or aggressive environmental effects. Methods such as the externally bonded reinforcement (EBR), despite of their advantages, have a problem known as the premature debonding of FRP from concrete substrate. In this method the surface of concrete is sanded and cleaned. After the preparation of the surface, the layer of epoxy is applied uniformly on the surface of concrete. Then, FRP is installed on the surface and saturated with epoxy. In other hand, a new strengthen method is the externally bonded reinforced on grooves (EBROG) method that consists of grooves on the surface of concrete. In this method, grooves with a proper length, width and depth are catted on the concrete surface; then the concrete surface and the grooves are cleaned with an air pressure. Later, grooves are filled with an appropriate epoxy. At the end, FRP sheets are installed with a proper epoxy on the concrete surface. In this paper, the effect of environmental conditions, including three alkaline environments with temperatures of 〖 23〗^° C, 〖40〗^° C and 〖60〗^° C, was investigated on the bond strength of FRP-to-concrete. The specimens were strengthened with two methods: EBR and EBROG. Samples were kept in environmental conditions for 3000 hours. Single-shear tests were conducted to evaluate the bond behavior of FRP-to-concrete. Experimental results showed that the specimens strengthened by the EBROG method - in the alkali environment with different conditions - experienced up to 50 % higher than ultimate bond loads compared with the specimens which were strengthened by the EBR method. In the EBR method, the bond failure mode changed from concrete delamination in laboratory condition to epoxy-concrete interface separation in alkali immersion with different temperatures. On the other hand, in the EBROG method environmental conditions had not effect on the mode of failure and more than 90% of specimens experienced FRP rupture. As a whole, the alkali environment caused a sudden drop in the bond strength of FRP-to-concrete substrate.},
Keywords = {EBR,EBROG,alkaline environment,temperature,},
volume = {17},
Number = {6},
pages = {195-204},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15456-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15456-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Mahmoodzadeh, Davood and Ketabchi, H.},
title = {Feasibility of groundwater resources cooperative management considering the environmental damages using ant colony optimization},
abstract ={In the recent decades, water demand has been increased specially in arid and semi-arid areas, led to the over-exploitation of water resources. Groundwater resources are important sources of water supply for domestic, industrial and agricultural consumption. Nowadays, over-exploitation from groundwater resources has increased the pressure on these sources which causes the major environmental damages. In this study, a cooperative game theory model is used to investigate how the cooperation of groundwater resources consumers influences the environmental damage and the benefit of stakeholders. The used model in the present study is developed for investigation of an optimal control problem including the variables of economic, environmental, agronomic, and hydrologic issues. Ant colony optimization method is used to flexible define and solve the simulation-optimization problem of this study which provides an ability to consider an extensive range of objectives and constraints. The results show that how uncontrolled pumping and over-exploitation in each aquifer affect on the stakeholders of the adjacent aquifers. Furthermore, the impacts on aquatic ecosystems are analyzed and presented as environmental damages. The obtained results demonstrate that in different areas, environmental damages are reduced under the coalition and effective cooperation condition among stakeholders and considering the environmental externalities in comparison with status quo. In the recent decades, water demand has been increased specially in arid and semi-arid areas, led to the over-exploitation of water resources. Groundwater resources are important sources of water supply for domestic, industrial and agricultural consumption. Nowadays, over-exploitation from groundwater resources has increased the pressure on these sources which causes the major environmental damages. In this study, a cooperative game theory model is used to investigate how the cooperation of groundwater resources consumers influences the environmental damage and the benefit of stakeholders. The used model in the present study is developed for investigation of an optimal control problem including the variables of economic, environmental, agronomic, and hydrologic issues. Ant colony optimization method is used to flexible define and solve the simulation-optimization problem of this study which provides an ability to consider an extensive range of objectives and constraints. The results show that how uncontrolled pumping and over-exploitation in each aquifer affect on the stakeholders of the adjacent aquifers. Furthermore, the impacts on aquatic ecosystems are analyzed and presented as environmental damages. The obtained results demonstrate that in different areas, environmental damages are reduced under the coalition and effective cooperation condition among stakeholders and considering the environmental externalities in comparison with status quo. In the recent decades, water demand has been increased specially in arid and semi-arid areas, led to the over-exploitation of water resources. Groundwater resources are important sources of water supply for domestic, industrial and agricultural consumption. Nowadays, over-exploitation from groundwater resources has increased the pressure on these sources which causes the major environmental damages. In this study, a cooperative game theory model is used to investigate how the cooperation of groundwater resources consumers influences the environmental damage and the benefit of stakeholders. The used model in the present study is developed for investigation of an optimal control problem including the variables of economic, environmental, agronomic, and hydrologic issues. Ant colony optimization method is used to flexible define and solve the simulation-optimization problem of this study which provides an ability to consider an extensive range of objectives and constraints. The results show that how uncontrolled pumping and over-exploitation in each aquifer affect on the stakeholders of the adjacent aquifers. Furthermore, the impacts on aquatic ecosystems are analyzed and presented as environmental damages. The obtained results demonstrate that in different areas, environmental damages are reduced under the coalition and effective cooperation condition among stakeholders and considering the environmental externalities in comparison with status quo.},
Keywords = {Groundwater resources management,cooperative approach,simulation-optimization,Environmental externalities,game theory,},
volume = {17},
Number = {6},
pages = {205-220},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15810-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15810-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Mehdizadeh, M. and Mamdoohi, Amir Rez},
title = {Role of Parental Environmental Norms on Use of Car in Elementary School Trips, a Quantitative Analysis},
abstract ={Reducing the environmental problems caused by transportation in various trip purposes (especially air pollution caused by cars use) in developed countries is of researches priorities. While in developing countries such as Iran, cultural aspects and environmental norms in discussing the use of cars in school trips (due to the complexity of decision making in school trip mode choice) well not identified. So far, in the field of educational trips have been discussed traffic and urban aspects (Strategies to reduce the volume of traffic), student’s health (encouraging children towards walking or cycling), traffic safety, accident prevention and mode use patterns. Also, less attention has been paid to environmental aspects and its quantification in school trips mode choice. Hence, this study analyses relation of parental norms towards environmental factors besides socio-economic factors in using schools trips modes of elementary students especially household private car what has been done in the frame of questionnaire with their parents. A questionnaire was designed and 1078 Questionnaires were distributed among Parents of students from grade one to three in nine elementary schools (including public and private boys and girls schools) in all districts of department of education in January 2014 (Return Rate: 80%) in Rasht. The questionnaire has three parts: socio-economic part, transport modes in school trips and parental norms towards environment and reducing car use. The questionnaire return rate was approximately 80%. After processing data, 735 questionnaires (more than 68% of total) were identified for analyzing and valid modeling. Based on the data achieved from this field questioning, Binary logit model were used to survey effectiveness and relationships of environmental norms components and socio-economic factors in use of household private car in school trips. Descriptive statistical analysis of the results of socio-economic variables (general characteristic of household) shows that 49.5% of observation were parents of boy student, 78.8% of sample were from public schools, 93.3% of fathers and 67.3% of mothers have driving license. Principal Component Analysis (PCA), with Varimax Rotation implied, a three-factor structure “personal norms ”, “Awareness of Consequences” and “Ascription of Responsibility” for parental environmental norms. Results show that parental environmental norms such as personal norms, concerns, feeling guilty about use of car and sense of responsibility towards the environment can play important role in reducing household private car use in escort of children to school. Also, direct and cross elasticity of logit model show that an increase of one percent of personal norms (Parental concerns about the environment and lees using of household private car) decreases the probability of choosing household private car mode to school by 0.86% and increases 0.15% choosing others school trips modes. An increase of one percent of awareness of environmental responsibilities in the utility of other school trip modes decreases 0.38% the probability of choosing household private car in school trips. Thus, such policies applied by the authorities in order to increasing parental awareness and sense of responsibility about importance of environmental issues with programs such as inviting parents to schools or cultural programs in the media can be effective in reducing car use in school trips.},
Keywords = {environmental norms,private car,elementary student,binary logit,questionnaire,},
volume = {17},
Number = {6},
pages = {221-231},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15720-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15720-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Mousavi, Shahram and Nourani, Vahid and Alami, Mohammad Taghi},
title = {Assessment of Chloride Concentration in Groundwater by Conjugation of Artificial Intelligence and Wavelet Transform Coherence Approaches},
abstract ={When groundwater is contaminated, removal of contaminants and the restoration of quality may be slow and sometimes, impractical. It can be harmful for human health, the ecosystem and can result in water shortage. Thus, simulation of contaminant transport can be an important task in hydro-environmental studies and consequently, it is necessary to develop the robust models which can determine the temporal forecast of pollution. For temporal modeling groundwater level and contaminant concentration (GLCC), several computational methods, namely, finite difference method, finite volume method, finite element method and boundary element method have been applied for numerical solution of governing physical-based partial differential equation (PDE). Although the physical-based numerical technique are widely used for temporal and/or spatial modeling of systems, some real-world conditions such as anisotropy and heterogeneity can have meaningful impacts on GLCC and restrict the usefulness of such methods. As a result, these method may be replaced by other techniques. In situation where there is no sufficient field data and output accuracy is preferred over perception of phenomena, a data-driven or black box model can be proper subsided. The uncertainty and complexity of the groundwater process have caused data-driven models such as artificial neural networks (ANNs) and adaptive neuro-fuzzy inference system (ANFIS) are widely used by hydrogeologists. Several studies have been performed to examine the susceptibility of artificial intelligence (AI) models for GFCT modeling. Wavelet transform coherence (WTC) is a technique for examination the localized correlation coefficient and their phase lag between non-stationary time series as a function of both time-frequency spaces. Furthermore, the cross-wavelet power is indicated as high common power of two time series and is found in time-frequency space by cross wavelet transform (XWT). Specifically, XWT investigates the regions in time-frequency space with large common power about a consistent phase relationship, and accordingly suggestion for causality between and time series. On the other hand, the WTC explores the regions in time-frequency apace in which and time series co-vary, but not essentially with high power. So, while analyzing two time series for evaluating both causality and local co-variance, the WTC is more suitable. In order to examine the applicability of the proposed AI-meshless model in real world conditions, the contaminant transport problem in Miandoab plain located in the northwest of Iran was considered as the case study. Miandoab plain, is located in a delta region of Zarrineh and Simineh Rivers. Urmia Lake in north of Miandoab plain, the largest salt-water lake in the Middle East, has been experienced climate change in early 2 decades. The wavelet transform coherence used in this study can be considered as a novel method for spatial clustering of piezometers, for detecting the interaction of aquifers in the plain and relationship between water level of the lake and GLs and CCs of piezometers located near the lake shore witch can present helpful information in GL and CC modeling. The results showed that the efficiency of ANFIS model was more than ANN model up to 30%. Reliability of ANFIS model is more than ANN model in both calibration and verification stages duo to the efficiency of fuzzy concept to overcome the uncertainties of the phenomenon.},
Keywords = {Groundwater,Contaminant Transport,Artificial Intelligence,Wavelet Transform,},
volume = {17},
Number = {6},
pages = {233-244},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-14417-en.html},
eprint = {http://journals.modares.ac.ir/article-16-14417-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Mirabi, Mohammad Hossein and Mansoori, Abbas},
title = {Assessment of Multi-Equation Mathematical Models of Turbulence in Estimation of Hydrodynamic Parameters at Submerged Jet},
abstract ={Three-dimensional submerged jet at a sudden expansion includes chaotic hydrodynamics. At a sudden expansion, secondary flows developed adjacent to the potential core of the jet generate turbulence, and the formed eddies cause energy transfer and dissipation and decline of fluid momentum in the zone of established flow. By utilizing an efficient mathematical model of turbulence, hydrodynamic flow parameters can be predicted with a good accuracy in various locations. This paper studies the three-equation mathematical models of turbulence, namely the Walters and Cokljat (k-kl-ω), and the seven-equation Reynolds Stress mathematical model of turbulence. Comparison between the results of computational fluid dynamics using Ansys Fluent software and experimental results shows that Reynolds Stress model of turbulence predicts the results with a higher accuracy. It can be concluded that this higher accuracy is due to the use of individual transport equations for each component of the stress tensor in the normal conditions of inhomogeneous and anisotropic turbulence. Kinetic energy, very high fluid momentum and pressure fluctuations are among characteristic of a submerged jets at a sudden expansion. How the energy is dissipated by the flow and how the secondary flow structures are generated need an extensive research. In the submerged jets, because secondary flows are developed in the vicinity of jet potential nuclear and eddies are generated in various sizes, the energy is received from the mean flow and will be being dissipated while being transferred. The dissipation process can be observed during the interaction between stress and strain fields of fluid elements (second-order tensor interaction). Formation of eddies with different sizes and decay of them into smaller structures prompt the process of turbulence diffusion. The energy-bearing eddies formed in the vicinity of the jet potential core are displaced by convection terms. After these eddies are displaced, they experience decay and reduction in size (Kolmogorov microscale) and finally disappear. Rotational dynamics around the jet potential core is of a great importance in terms of flow kinetic energy dissipation; it is why the sudden expansion ratio is a number that represents the range of rotation. Therefore, understanding the flow behavior as well as how the resulting energy is generated and dissipated requires the flow parameters to be known. In order to predict the most accurate (closest to reality) values of the hydrodynamic parameters of a submerged jet, it is necessary to utilize an efficient mathematical model. Among the proposed models of turbulence, only the multi-equation Reynolds stress mathematical model has included anisotropy. Based on what have been stated so far, it seems that the existence of discrete transport equations for each component of stress tensor for a fluid and turbulence kinetic energy dissipation as well as comparison with experimental results provide the possibility of acceptable accuracy in predicting the flow hydrodynamic parameters. In this model, the term of turbulence kinetic energy generation from the mean flow, energy dissipation term, and pressure-strain term transferring the turbulence kinetic energy toward different directions of the coordinate axes are among the very important elements of the transport equation.},
Keywords = {Submerged jet,Multi-Equation Mathematical Models of Turbulence,Computational Fluid Dynamics,},
volume = {17},
Number = {6},
pages = {245-258},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-17018-en.html},
eprint = {http://journals.modares.ac.ir/article-16-17018-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {Nosrati, M. and golshani, Aliakbar and Barani, Omid rez},
title = {Numerical modeling of hydraulic fracturing in a poroelastic medium using cohesive elements},
abstract ={From oil and gas engineering point of view, one of the challenges in low permeable or damaged wells is improving the productivity. There are different methods to increase the productivity of low permeable wells and one of the most efficient one is hydraulic fracturing. In this study, two-dimensional modeling of hydraulic fracturing using finite element method and cohesive element approach through traction-separation law has been performed. This approach avoids the singularity in the crack tip and the cohesive zone fits naturally into the conventional finite element method. Hydraulic fracture is assumed to propagate in a poroelastic and permeable medium with a constant injection rate and under quasi-static conditions and the criterion for fracture initiation is quadratic nominal stress criterion. Also as a propagation criterion, Benzeggagh Kenane (BK) approach has been considered. Two types of elements have been implemented in the model which are 4-node bilinear displacement and pore pressure reduced integration and 6-node displacement and pore pressure two- dimensional cohesive element. Cohesive elements have three degrees of freedom that two of them are in X and Y directions and one of them is pore pressure. Mesh size in the near fracture region is small enough to consider the stress and pressure distribution efficiently and avoid any problem in convergence. Meantime, to decrease the computation cost the mesh size gradually increases from fracture area to the boundaries. Also, to increase the accuracy of the model, the time steps for fracture propagation is 0.01 second. In addition, the effect of fracturing fluid has been directly included in the model which means that the fluid pressure would be applied along the fracture without any simplifying assumption. To validate the model, the results have been compared with KGD approach. The results indicate that in the initial steps the pressure at the wellbore wall is high which decreases with time significantly and eventually it gets a steady and uniform trend. In other words, in the initial steps, the fluid pressure should be high enough to overcome the hoop stress around the wellbore and after some injection periods, the fracturing fluid pressure would reach the breakdown pressure and the fracture starts to initiate and propagate. It is clearly observed that increasing the injection rate would lead to faster propagation of hydraulic fracture and in the models with higher injection rate the fracture tends to grow in the propagation direction. This indirectly means that increasing the injection rate would affect both opening and length of the hydraulic fracture which can result in increasing the productivity. The results reveal that the peak of the normal effective stress profiles corresponds to the fracture tip position, where the fracture opening is zero,and the peak value equals the cohesive strength of the material,as expected.Moreover,with increasing thedistance from the fracture tip,the stress decreases rapidly and approaches the initial stress value. The way that Young’s modulus affects the overall characteristics of hydraulic fracture implies that higher Young’s modulus would lead to longer fractures. In other words, formations with higher Young’s modulus can be fractured easily but the opening of the hydraulic fracture would reduce at the same time. This also indirectly means that Young’s modulus would play an important role in the productivity.},
Keywords = {Hydraulic Fracturing,Finite Element,Fracture Mechanics,Cohesive Element.,},
volume = {17},
Number = {6},
pages = {259-268},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-12824-en.html},
eprint = {http://journals.modares.ac.ir/article-16-12824-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}
@article{
author = {NazariAliAbady, Kh. and Akhtari, A.A.},
title = {Effect of Vertical and Curve blocks on Hydraulic Jump Characteristic in Diverging Rectangular Sections With FLOW-3D Software},
abstract ={The hydraulic jump phenomenon is one of the most common phenomena in open channels. Hydraulic jump is a transition state from supercritical to subcritical flow regime, which normally occurs in conjunction with hydraulic structures, such as spillways, weirs, and sluice gates. A hydraulic jump phenomenon serves a variety of purposes, for instance, to dissipate the energy of flow to prevent bed erosion and aerate water or to facilitate the mixing process of chemicals used for the purification of water. Stilling basins are one of the most common structures for energy dissipation of flow with high velocities. The stilling basin has been accepted to be the most powerful hydraulic structure for the dissipation of the flow energy. The size and geometry of the stilling basin affect the formation of flow patterns, which can be influential for hydraulic performance of the whole system. The depth of water after the jump is related to the energy content of the flow, and any reduction in energy content with increased energy dissipation in the jump will reduce the required depth of flow after the jump. Sometimes these basins are supplied with appurtenances that increase the overall roughness of the basins. This in turn increases the energy dissipation, decreases the sequent depth, and requires a shorter basin for the full development of the hydraulic jump. There are plenty of research studies in the literature regarding the classical hydraulic jump in the usual rectangular straight stilling basin, but less for the hydraulic jump in other cross section shape of basins. Expanding gradually basin with the rectangular cross section acts as two separate hydraulic structures including stilling basin and transition. In this type of structures not only the transition can be eliminated, but the length of the basin will be also much smaller than what is designed for the usual straight basins. Researchers’ studies show that divergence in stilling basins reduce the sequent depth and the length of the jump while increasing the energy losses compared to the classic jumps. In this research, numerical simulation of the hydraulic jump was performed in divergence rectangular sections, and compared with the results of the laboratory, making use of the FLOW-3D software and the standard k-ԑ and RNG k-ԑ turbulence models. The effects of Vertical and Curve blocks on the specification of hydraulic jump were evaluated. The results showed that the standard k-ԑ turbulence model was able to predict the water level profiles in the hydraulic jump in divergence rectangular sections with appropriate and acceptable coincidence. Results showed that the mean relative error of water surface obtained from numerical model and measured values is about 3.55 percent. Also the numerical model showed the vortices that were accrued because of diverging walls as well as experiment investigations. The results show that creating the vertical blocks, reduces the sequent depth as much as 46.27 % and the length of the hydraulic jump as much as 17.64%, while increasing the energy loss as much as 31.57%, compared to the classic hydraulic jumps. The results also show that creating the Curve blocks, reduces the sequent depth as much as 69.76 % and the length of the hydraulic jump as much as 35.29%, while increasing the energy loss as much as 32%, compared to the classic hydraulic jumps.},
Keywords = {Diverging Hydraulic Jump,Curve blocks,Vertical blocks,k-ԑ Turbulence model,FLOW-3D software,},
volume = {17},
Number = {6},
pages = {269-280},
publisher = {Tarbiat Modares University},
url = {http://journals.modares.ac.ir/article-16-15238-en.html},
eprint = {http://journals.modares.ac.ir/article-16-15238-en.pdf},
journal = {Modares Civil Engineering journal},
issn = {2476-6763},
eissn = {2476-6763},
year = {2018}
}