Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
The application of activated carbon produced from used newspaper in the removal of methylene blue dye from aqueous solution: isotherm, kinetic and thermodynamic study
1
9
FA
fariba
khalili nadji
Activated carbon is widely used at various industrial processes such as water and wastewater industries. Activated Carbon (AC) is an adsorbent which is mostly employed for removing dye from aqueous solutions because of its excellent adsorption properties. Therefore, AC is used in the adsorption process in order to remove different pollutants from the wastewater, especially colored contaminants. however; the use of commercial grade of activated carbon is faced with difficulties due to the high price of raw materials. The used newspaper found as a main component of solid wastes can be used for producing of activated carbon. One of the most important industrial pollutants, especially in textile industries, is the dyes that even at low concentrations of one parts per million (ppm) are recognizable by naked eyes. One of the mostly consumed materials in the dye industry is Methylene Blue (MB) which is used for cotton and silk dyeing. Up to now, a great number of methods have been proposed in order to remove dyes from the industrial waste water, among which adsorption is the most acceptable due to its cost effectiveness and the possibility of usage in large scales. The aim of this study is to evaluate the performance of activated carbon produced from the used newspaper for the removal of methylene blue dye in aqueous solution. KOH solution (weighted ratio of 1:3) was used to activation. The carbonization process was applied at 500˚C with the rate of 17˚C/min. After carbonization, the sample was cooled down to room temperature and then washed with distilled water until the pH of the filtered water was stabilized at 7.5. N2 adsorption at 77K is used to characterize the produced activated carbon using BET isotherm. To evaluate the performance of methylene blue dye removal, the Langmuir, Freundlich, Temkin and Redlich-Peterson isotherms with pseudo-first and pseudo-second order and inter-particle diffusion kinetic models were used. Thermodynamic parameters such as enthalpy (ΔΗ˚), entropy (ΔS˚) Gibbs free energy (ΔG˚) were also calculated. Based on the results, the values of SBET and VTOTAL were obtained 66.01 m2/g and 0.063 ml/g, respectively. According to the R2 and sum of squares for error (SSE%) values and regression curves, the optimum isotherm and kinetic model were determined Freundlich and pseudo-second order ones, respectively. In addition, qmax constant was obtained 68.03 mg/g for Langmuir isotherm. Kinetic parameters showed the adsorption of methylene blue dye on the activated carbon is endothermic and spontaneous. Also, (ΔG˚) in physical adsorption was changed from 0 to -20 kJ/mol, while the amount of the chemical adsorption will changed between -80 to -400. Finally, the activated carbon obtained from used newspaper in this study showed a better specific surface area and adsorption capacity for methylene blue dye adsorption in compared with other grades. Thus, the production of activated carbon from used newspaper should be considered as a cheaper and more effective alternative.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Cyclic Behavior and Backbone Curves for Batten Columns
11
22
FA
Mohammad ali
Jafari Sahnehsaraii
Assistant profesore-Niroo Research Institute
Behrokh
Hosseini Hashemi
Associate professor, International Institute of Earthquake Engineering and Seismology (IIEES)
In this paper, the cyclic behavior and available ductility of batten columns subjected to constant axial and cyclic lateral load (seismic condition) and their failure mode are evaluated numerically using nonlinear finite element analysis. The column specimens were steel I-shape sections and were analyzed as an equivalent cantilever column. Batten columns are compression members composed of two or more similar longitudinal components (chords) that are connected at points along their length with batten plates as transverse connectors. These connectors ensure that the column behaves as one integral unit to achieve maximum axial capacity. In the past decades, many research activities were conducted on the buckling problem of batten columns. When a batten column is subjected to lateral load or bending moment about its hollow axis (axis perpendicular to battens) in addition to axial compression, the additional internal actions will be imposed to its members (chords and battens). In this case, it is expected that the batten column will have different behavior and failure modes. If the lateral load or displacement is due to seismic actions, more complexities will exist in the column behavior due to nonlinearities and its post-failure response. Few researches were reported about the behavior of batten columns in seismic conditions and their ductility. In this research, the backbone curves for batten columns have been also developed based on their cyclic response. The component backbone curve represents the nonlinear behavior of component in plastic hinge locations and was used in the nonlinear pushover analysis. The backbone curve for some structural components has been found in many standard and guidelines of seismic evaluation like as FEMA356. Using the backbone curve, the available ductility of column considering its post failure response under cyclic lateral loads, could be evaluated. The backbone curve for batten columns does not exist in any guideline or research reports. Because of differences between behavior and failure modes of batten and solid web columns under seismic action, it was expected that their backbone curves had been substantially different. In this research, cyclic response of batten columns with different geometries have been investigated subjected to cyclic lateral and 3 level of constant axial load. Using cyclic curves, the backbone curves of considered batten columns have been developed. The results show that the available ductility of batten columns is considerably low compared with solid web columns. The failure mode of batten columns is local buckling of bottom chords (in flanges and web) in combination with overall buckling of these chords symmetrically. It is also shown that the backbone curves of batten columns are different from solid web columns. The backbone curves of batten columns are semi-ductile (Type 2) based on FEMA356 classification and don’t have any residual strength. Finally, a conservative backbone curve has been proposed for engineering applications.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Intelligent hydraulic deign of tunnel type sediment excluders
23
37
FA
Masoud 1
Raphiey
Masoud 2
Ghodsian
Tarbiat Modares University
٭ Amir Ahmad
Dehghani3
of Agricultural Sciences and Natural Resources
The sediment excluders are provided on the barrages or diversion weirs in the river pocket adjacent to the head regulator to minimize sediment entry in to the canal water. On rivers, the excluders have to deal with alluvial material being transportd by the river. Excessive sediment load can cause damage in a variety of ways which result in many serious problems such as meandering of stream, reduction of channel capacity, silting up of canal, damage to power units and obstruction to navigation. Different types of sediment extractors/ excluders, such as tunnel type, vortex tubes, rectangular settling basins and vortex type settling basins are ofthen employed for this purpose. A tunnel-type sediment excluder is commonly used at the headwork of a canal for preventing excess sediment entry in to the off-taking canal. In such type of excluders, the sediment-laden water, which flows mainly near the bed, is made to flow through the tunnels provided at the bed and the sediment-free water in the top layers is allowed to enter the off-taking canal. It may be then discharged back into the river downstream through the undersluice bays. Comparatively sediment-free water in the top layers is allowed to enter the canal. The only hydraulic principle utilized in its design is that energy loss is kept to a minimum and a minimum velocity of flow is ensured through the tunnel for the non-deposition of the coarse material
In the method recommended by Garde and Pande (1976) and Kothyari (1999) for design of tunnel-type sediment excluders, the main objective is to design a tunnel which is able to flush maximum of sediment load through the tunnel by minimum of excluder discharge and minimum of blockage hence considering all restrictions and constraints for design of such structures.
In the current research it was tried to achieve an optimum design using fuzzy logic abilities and searching the solution domain by an intelligent search method (Genetic Algorithm) which is able to pass the local optimums and find the global optimum. GA considers many points in the serach space simultaneously and has been found to provide a rapid convergence to a near optimum solution in many types of problems. Then optimal designs of GA and Direct-Search method were compared with some of projects in India (i.e. Ganga, Sarda and Eastern Kasi) which were design using traditional methods. A fuzzy AHP (Analytic Hierarchy Process) approach was used for assessing the weight of efficiency, blockage and sediment excluder discharge in goal function. AHP is particulary usefull for evaluating complex multi attribute alternatives involving subjective criteria.The fuzzy AHP approach allows a more accurate description of the decision making process. The triangular fuzzy numbers were used to build the comparision matrices of AHP based on pairwise comparision technique.The results show that the Genetic Algorithm method gives better results in compare with direct search technique. The result also show that the efficiency of tunnel-type sediment excluders are high enough in both optimal design and traditional methods, but sediment blockage percent in propose optimal design is less than correspond design values using
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Comparing Seismic Performance of Yielding Damped Braced Frames with Mild and Low-Yield Steel in Typical Steel Buildings
39
52
FA
Seyed Mehdi
Zahrai
the University of Tehran
Sobhan
Arman Nikoo
مقایسه عملکرد لرزه ای میراگرهای تسلیمی مرکزی از فولاد ساختمانی و فولاد با حد جاری شدن پایین در ساختمانهای فولادی متداول سید مهدی زهرائی دانشیار قطب علمی مهندسی و مدیریت زیرساختهای عمرانی، دانشکده عمران دانشگاه تهران mzahrai@ut.ac.ir سبحان آرمان نیکو کارشناس ارشد مهندسی زلزله- پژوهشکده ساختمان و مسکن sobhan.arman@gmail.com در این تحقیق به مقایسه عملکرد لرزه ای میراگرهای تسلیمی مرکزی با درصد بازشوی 20 تا 30%، از فولاد ساختمانی و فولاد با حد جاری شدن پایین در ساختمانهای فولادی متداول پرداخته شده است. بدین منظور قابهای یک طبقه با استفاده از نرم افزار ANSYS تحت تحلیل قرار گرفته اند و با استفاده و استناد به نتایج حاصله ابتدا همین سازه ها با مقاطع و هندسه مشابه در نرم افزار SAP2000 مدلسازی شده و پس از مطابقت نتایج، مدلهای قابهای فولادی 5 و 7 طبقه در نرم افزار SAP2000 به روش تحلیل بار افزون تحت تحلیل قرار گرفته اند. نتایج به دست آمده نشان دهنده بهبود رفتار لرزه ای این قابها در صورت استفاده از فولاد با حد جاری شدن پایین به جای فولاد معمولی در سیستم قاب مرکزی می باشد. افزایش سختی قاب با میراگر حداقل به میزان 5/1 برابر، کاهش تغییرمکان حد تسلیم حداقل به میزان 50 درصد، بهبود منحنی های هیسترزیس و همچنین تشکیل عمده مفاصل پلاستیک بر روی اعضا میراگر تسلیمی مرکزی ازجمله نتایج بدست آمده می باشد. کلید واژه ها: میراگر تسلیمی مرکزی، فولاد ساختمانی، فولاد با حد جاری شدن پایین، منحنی هیسترزیس، مفصل پلاستیک. Comparing Seismic Performance of Yielding Damped Braced Frames with Mild and Low-Yield Steel in Typical Steel Buildings Seyed Mehdi Zahrai Associate Professor, Center of Excellence for Engineering and Management of Civil Infrastructures, School of Civil Engineering, the University of Tehran, mzahrai@ut.ac.ir Sobhan arman nikoo M.Sc. in Earthquake Engineering, Building and Housing Research Center, sobhan.arman@gmail.com In this paper, the seismic performance of typical steel buildings with yielding damped braced frames of mild steel (MS) and 20-30% opening is compared to that having low yield steel (LYS). For this purpose, one story frames are first modeled by "ANSYS" software, then calibrating the results, these structures are carefully modeled with the same geometry and section using "SAP2000" software. Using the validated models, five and seven story frames are analyzed by the push over method in "SAP2000" software. The results demonstrate that the seismic response of these frames improves if low yield steel instead of mild steel is used in central frame system. The results for the frame with damper included: stiffness increase minimum 1.5 times, at least 50% reduction of yielding point displacement, hysteretic curves improvement and formation of the main plastic hinges on the members of the yielding damped braced frames. Key words Yielding Damped Braced Frames, Low Yield Steel, Mild Steel, Hysteretic Curve, Plastic Hinge.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Evaluation of non-linear cyclic behavior of CONXL moment connection with different detail in the column and optimizing the arrangement of bolts
53
65
FA
Farhood
Shahidi Imam jomeh
Alireza
Rezaeian
Majid
Jamal-Omidi
Farhad
Shahidi Imam jomeh
Box-columns are suitable members for structures with moment frames in two directions but performing the internal continuity plate in them causes some practical troubles. Details of the new proposal to alleviate this problem in box-columns is CONXL connection. This connection includes a set of Collar Flange Top (CFT), Collar Flange Bottom (CFB), Collar Corner Top (CCT), Collar Corner Bottom (CCB) and when the depth of the beams is more than 460 mm, Collar Corner Middle (CCM), Collar Web Extension (CWX) (only in the face of beam to column connection) and also a set of diagonal pre-tensioned high strength bolts (45 degrees angle), which collectively make up CONXL node. The bolts and collars performance make up a rigid diaphragm around the column. All collar flanges top and bottom are connected to the beam by means of groove welding with complete joint penetration, and the connection of collar web extension to the beams and that of collars corner to the column walls is made by fillet weld; collar corners are connected to each other through groove weld in factory and the pieces are just assembled in worksite. The objectives of presenting these details are industrializing, removing weld in workplace, removing continuity plate, enhancing quality, speeding up the construction, and simplifying the inspection. Through the distribution of force among collar systems, forces are transmitted from beams to the columns. The aim of this study is to numerically study the seismic behavior of CONXL connection without filler concrete of columns and to reduce the number of collar bolts with different arrangements. In order to reach this purpose, the numerical results of specimens; RBS and Kaiser bolted bracket (KBB) connection are compared to experimental results to verify the modeling and analyzing and good agreement is observed between numerical and experimental data. Afterward nine specimens of CONXL moment connections in box-columns not filled with concrete whit axial force in single, planer and bi-axial loading conditions with different arrangement of bolts are studied and their performances are evaluated. Results showed that seismic behavior of specimens with beam section depths equal or less than W30 series under cyclic loading, even with reducing the number of bolts to 16 numbers, is suitable in the over 0.04 radian rotations. Also, use of 16 numbers of bolts in connections with W30 series of beams, when it would be appropriate that use for corner connections (Single sided loading), and the specifications of ASTM-A36 for beams material to be used. Also, whatever the position of bolts to be outer than in collar flanges, axial strain in the bolts shank is bigger and its slip is less. The optimal position of the bolts is near the middle of the collar flanges. The results also showed that seismic behavior of all specimens with columns without concrete filling is appropriate and the column will remain without any remarkable local buckling in over 0.04 radian inter-story drift angle.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Numerical Evaluation of the Effect of Vertical Component of Near-Field Earthquakes on the Dynamic Behavior of Embankment Dams, A Case Study: Alborz Dam
67
79
FA
reza
sadighi hashtchin
asskar
Most of the research has been concentrated on the effects of the horizontal components of near-field earthquakes on the dynamic behavior of the embankment dams. In this paper, the effects of the vertical components will be considered. One of the important characteristics of the near-field ground motions, is the noticeable vertical component with the high frequency content that can exceed considerably, in many cases, the horizontal component of the same earthquake. So far, few studies have been done in this area. In order to investigate the effect of the vertical ground motion on the dynamic behavior of embankment dams, a two dimensional numerical model of the Alborz dam is analyzed by using finite difference method which is used in FLAC2D code. It should be noted that the Alborz dam is a rockfill type with clay core and a maximum height of 78 m located on the Babol River in the north of Iran. The Mohr Coulomb elastic perfectly plastic constitutive model was used to simulate the stress-strain behavior of the dam body and its foundation during the static and dynamic loading. Steps of modeling are as follow: At first stage, construction was carried out in 16 layers. At this step, coupling analysis were done in order to simulate the consolidation and build up of pore pressure in clayey core, with respect to the real time of construction for each layer. Then the analyses were continued to modeling of the impounding. So at this stage the reservoir was raised to the normal water level and the model were analyzed to the steady state seepage condition. Records of near-field and far-field were selected from the same earthquake to provide better and more accurate comparison. Before applying the earthquake records to the base of the foundation in the model, they must be modified. So deconvolution analyses were done by using SHAKE2000 code in order to get the target motion with peak ground acceleration of 0.52g at the surface of the foundation (maximum credible earthquake level at the site of Alborz dam). In addition filtering process, baseline correction and conversion the acceleration time history to the stress time history were done. Results of analysis show that the vertical component of near-field ground motion has considerable effect on the magnitude of strains and deformations including: increasing the settlement of the dam crest to about 45 percent, increasing the deformation of the horizontal axis of the dam, reduction of the magnification factor of the dam crest and especially in the case of near-fault, which the occurrence of near-field earthquakes is more probable. Therefore, this issue should be considered in locating the embankment dams regarding the seismic potential and the distance from the fault, and in the design of them.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Multivariate Flood Frequency Analysis Using Copula with Parametric and Nonparametric Marginal Distribution Function
81
92
FA
MohammadSadegh
Abbasian
Soheil
Jalali
Many variables under study in hydrology are continuous and random; hence, it necessitates using probability and statistics sciences to study them. In a specific classification, variables are categorized to be either explanatory or response variable. An explanatory variable is defined as a variable which explains or predicts changes in the value of another variable, while a response variable is a variable whose prediction of its changes is desired under the effect of other variables. Due to the mentioned definition, a response variable may depend on one or more explanatory variables. Therefore, in the first case the response variable is intrinsically univariate and in the second case is intrinsically multivariate. If it is known that a hydrological response variable is intrinsically multivariate, multivariate statistical approaches must be employed, especially in the case of dependency among explanatory variables, because it has been widely warned that implementing univariate statistical approaches may result in over/under estimations. According to the fact that flood is an intrinsically multivariate event, it is essential to employ multivariate approaches to analyze it. The most important characteristics of flood are peak discharge, volume and duration. A traditional approach in multivariate analyses is to use classical multivariate distribution functions with parametric marginal distribution functions. However, both classical multivariate distribution functions and parametric distribution functions face substantial limitations. Among the limitations attributed to classical multivariate distribution functions, one may refer to the necessity of identifying marginal distribution functions and their parameters and equality of the kind of marginal distribution functions as the most important limitations. Also in the use of parametric distribution functions for marginal variables, an assumed distribution function is used to describe the distribution of data, while perhaps the assumed distribution function does not accurately describe the real distribution of data. The aim of this article is to establish joint distributions of different combinations of flood characteristics and corresponding return periods. Hence, firstly marginal distribution functions are chosen among parametric distribution functions and non-parametric distribution functions, which are not restricted to estimation of some parameters. Then joint analyses of flood variables are performed using copulas, which do not confront limitations of classical multivariate distributions. Finally, having found and appropriate copula for each combination of flood characteristics, joint return periods are calculated and contour plot of joint return periods are plotted. Joint return periods of flood characteristics can be used by water resources decision makers and engineers as a hydraulic design criterion and provide useful information for risk analysis. In this article, joint analyses of flood variables are performed using copulas, which do not confront limitations of classical multivariate distributions, such that marginal distribution functions are chosen among parametric distribution functions and non-parametric distribution functions, which are not restricted to estimation of some parameters. It should be mentioned that the R language has been utilized as the primary tool in order to perform calculations and draw diagrams. Keywords: Flood Frequency Analysis, Joint Return Periods, Copula, Non-parametric distribution
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Technical and economic evaluation of pavement rehabilitation on vehicle fuel consumption costs
93
102
FA
Ebrahim
Shoormeij
M.Sc. Student, Department of road and Transportation Engineering, K.N.Toosi University of Technology.
Mansor
Fakhri
Assistant Professor, Department of road and Transportation Engineering, K.N.Toosi University of Technology.
Evaluation of Vehicle Operating Costs (VOC) are necessary in pavement management. Vehicle Operating Costs including Fuel consumption costs, accident costs, oil consumption costs, maintenance costs and vehicle depreciation that often paid by road users. Vehicle Fuel consumption costs, is one of the important components of the life cycle costs analysis that it is typically between 20 to 40 percent of the total vehicle operating costs. There are many factors that effect on vehicles fuel consumption. Vehicle type, pavement surface condition, road geometry, vehicle speed and,…effect on vehicle fuel consumption and pavement life cycle costs. Pavement surface condition is one of the factors that effected on vehicle fuel consumption. Pavement roughness, skid resistance and the pavement deterioration are the components of the pavement surface condition. Using of pavement maintenance alternatives at the appropriate time, in addition to improve the pavement surface condition, reduce the vehicle operating costs and vehicle fuel consumptions. The goal of this research is to evaluate the effect of pavement maintenance in a 10 years analysis period on vehicle fuel consumption costs using HDM-4 software. HDM-4 is an application software for pavement management and evaluation of pavement surface condition that has been developed by the world bank. This software needed a serious of input data to analysis. This input data are divided in to four parts, including road networks, vehicle fleets, road works (repair and rehabilitation standards), and HDM-4 Configuring (define standards criteria for each of the variables in the program). For this purpose, effect of pavement maintanence and rehabilitation evaluated in 1170 km of Khozestan province road networks. This rehabilitation alternatives including routine maintenance, single surface dressing, 50 mm overlay, 100 mm overlay and, pavement reconstruction. In this research each rehabilitation approaches was used Separately as a pavement maintenance alternative. In rehabilitation approaches it was supposed that after performed pavement rehabilitation IRI reached to 1.5 m/km. According to HDM-4 ranking this IRI is good. Results of this research showed that, pavement surface conditions effect on vehicle fuel consumption. In other words, improving pavement surface condition cause to reduced vehicle fuel consumption. With applying routine maintenance (crack sealing and patching) there was no change on reducing the vehicle fuel consumption. But, with applying single surface dressing vehicle fuel consumption was reduced during the pavement analysis period. The reduction in vehicle fuel consumption after applying pavement rehabilitation is varies for different type of vehicles. Although the costs of rehabilitation alternatives are more than the cost of routine maintenance, but the economic savings in reduction of vehicle fuel consumption costs are more than the costs of the pavement rehabilitation alternatives in the long terms analysis. According to the result, economic saving from the single surface dressing alternative is more than the other pavement maintenance and rehabilitations alternatives. It was concluded that using rehabilitation in the appropriate time could cause reduction in fuel consumption and resulted in cost saving.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Damage Detection in Beams Using Static Deflection measurements and Statistical Hypothesis Testing
103
113
FA
Ali
Zare Hossein Zadeh
Seyed Ali
Seyed Razzaghi
Building structures begin to deteriorate once they are built due to harsh environment such as earthquake. To inspect present buildings and bridges following major disastrous events, such as earthquakes and hurricanes is often time-consuming and of high expense. This is also the case in regular operating conditions. Indeed critical members and connections are hidden under cladding and other architectural surface covers. This study aims to propose a novel method for identification of damages occurred in beams based on deflection under static loading. In this paper damage location on a beam is determined using statistical hypothesis testing applied on the deflection of the beam. It is worth mentioning that the statistical hypothesis testing is an appropriate method for statistical inference which can be used to judge a claim concerning an event in regards to different scenarios and possibilities. The statistical claim which would be analyzed is that damage is present among elements of the beam. Deflection of beam as a derivation of stiffness will be utilized here. Hence the basic idea in this study; to locate damages, is behind of calculating the difference between measured and estimated deflection of nodes of each element in both intact and damaged structures. Elements damage can be specified by applying damage index which is defined as D(x). Element’s damages can be judged through the damage index sign in two nodes of every element: The element will be considered damaged if the index is positive for both nodes of middle element or it is positive in only one node of element leading edges of fulcrums. To illustrate the efficiency and robustness of proposed method three different examples are considered. First example is a simple beam with five different scenarios including single and multiple damages. Second example is also presented to show comparison of the proposed method with the study by Abdo [18] and finally third instant is considered for showing reliability of the method in different beam types. For all of the examples, the deflection of damaged beams is recorded via sensors under only one state of static loading and the statistical parameters of the undamaged beams are generated under several static loading. Then by calculation of damage index, we can decide about damage locations. All examples show good performance of the novel method in damage localization. The most important result obtained from these examples is that, the more fine mesh, the better and the more accurate performance of the method. Of course this assertion is more important in the elements leading edges of fulcrums. Further, the performance of this method is demonstrated through damage simulation where the measured data are contaminated with noise and hence to evaluate the stability of the proposed method against various noise levels, scenarios are considered with different such levels.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Demand and Capacity of Structural Elements for Steel Moment Resisting Frames in Near Field of Fault
115
125
FA
davood
abdollahzadeh
Mohsen
Gerami
Experiments from disaster earthquakes showed, from Forward directivity, Backward directivity and Filing step effects in near fault strong motion, Forward directivity has more severe effects on engineering structures. In near fault regions when rupture propagation of fault is toward to the construction site and velocity of strong motion waves is approximately equal to rupture propagation speed, the velocity time history record of ground that is normal to the fault surface has 1 to 3 long period pulses with high magnitude. This future causes to impose more demands of strength and ductility to structures located normal to the fault line in near field of fault. Also average amplitude of response spectrum of near fault earthquakes are about 1.1 to 2 times more than average response spectrum of regions located far from fault. To estimation of forward directivity effect on structural elements, in this study variation of demand and capacity of beams and columns of steel moment resisting frames are studied under effect of forward directivity with variation of models height. So the variation of strength and ductility demand of structure elements have been estimated under effect of forward directivity based on FEMA356 instruction by 100 time history nonlinear dynamic analyses for 5 structural models. The modes were steel moment resisting farms with 3, 5, 7, 10 and 15 stories height. To studding about effect of forward directivity on beams, maximum nodal rotation, maximum absolute moment and seismic performance of beams studied. Results showed forward directivity causes to increase nodal rotation 1.1 to 1.7 times more for low-rise models (7 stories and less) and 1.4 to 3.2 times more fore high-rise models. The maximum moment of beams is increased 2 to 16% for low-rise models and 10 to 50% for high-rise models. In life safety level, demand to capacity ratio of performance level of beams is increased between 1 to 1.6 times more for low-rise models and 1.2 to 3.2 times more for high-rise models. Also it has been indicated that forward directivity has not any effects on beams ductility. Studding on forward directivity effects on columns showed because of interaction between axial force and moment of columns, forward directivity is able to effect on moment capacity and ductility of columns. So forward directivity increases 2 to 20% axial force of columns related to height of models and location of columns. Results illustrate axial force increasing about 20% causes to decrease 12.5 to 50% of moment strength capacity of column and also it can decreases 20 to 50% rotation ductility of columns. On the other hand forward directivity causes to increase moment demand of columns about 30 to 56% for high-rise models. Conclusions showed forward directivity effects causes to increase demand to capacity ratio of structural elements about 1.1 to 1.75 times more for low raise models (7stories and less) and 1.5 to 5 times more for high rise models. Also it is considered that aspect ratio of structure has a direct relationship to amplification of forward directivity effect on columns.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
A Numerical Study on Bearing Capacity of Ring and Circular Foundations on Granular Soils Reinforced by Grid-Anchor System
127
136
FA
Mansour
Mosallanezhad
هیات علمی
Abstract: Soil reinforcement is one of the soil improvement techniques. Over the last four decades, a large number of researches have been carried out in order to obtain the reinforcement type and the bearing capacity improvement of the reinforced soil. A new reinforcement type called Grid-Anchor (G-A) has been recently invented which is made of geogrids by adding polymer anchors to it. In this study the bearing capacity of ring and circular footings located on granular soils reinforced with the G-A is investigated using numerical analyses. Commercial finite-element software PLAXIS is employed to perform the simulations. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, for each foundation were investigated. The effect of reinforcement stiffness for two types of footing has been investigated. A comparison between the results obtained for the G-A and geogrid reinforcement systems and unreinforced soils is demonstrated as well. Abstract: Soil reinforcement is one of the soil improvement techniques. Over the last four decades, a large number of researches have been carried out in order to obtain the reinforcement type and the bearing capacity improvement of the reinforced soil. A new reinforcement type called Grid-Anchor (G-A) has been recently invented which is made of geogrids by adding polymer anchors to it. In this study the bearing capacity of ring and circular footings located on granular soils reinforced with the G-A is investigated using numerical analyses. Commercial finite-element software PLAXIS is employed to perform the simulations. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, for each foundation were investigated. The effect of reinforcement stiffness for two types of footing has been investigated. A comparison between the results obtained for the G-A and geogrid reinforcement systems and unreinforced soils is demonstrated as well. Abstract: Soil reinforcement is one of the soil improvement techniques. Over the last four decades, a large number of researches have been carried out in order to obtain the reinforcement type and the bearing capacity improvement of the reinforced soil. A new reinforcement type called Grid-Anchor (G-A) has been recently invented which is made of geogrids by adding polymer anchors to it. In this study the bearing capacity of ring and circular footings located on granular soils reinforced with the G-A is investigated using numerical analyses. Commercial finite-element software PLAXIS is employed to perform the simulations. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, for each foundation were investigated. The effect of reinforcement stiffness for two types of footing has been investigated. A comparison between the results obtained for the G-A and geogrid reinforcement systems and unreinforced soils is demonstrated as well
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Effect of Congestion Pricing on Users' Mode Split Using Stated Preference Technique
137
148
FA
B.
mirbaha
m.
saffar
s.a
abrishame
S
sharafaty
Congestion pricing is one of the main strategies for demand management in urban areas. One of the main questions for decision makers, for implementing this strategy, is the effect of congestion pricing on users' mode split. For defining this, the willingness to pay of users should be estimated. In another word, we should know that how much users still will to pay for using their personal cars and how they intend to perform their mobility according to various prices. Previous studies had pay less attention to paratransit mode according to pricing. In this research, the effect of congestion pricing on users' mode choice has been investigated. The restricted traffic zone of Tehran has been selected for case study. Due to impossibility of direct observation, the stated preference method was applied for data gathering. Various pricing scenarios, based on experimental design concept, were defined and several types of questionnaires were designed. In these questionnaires, 3 types of data were asked from interviewees including trip chain of the users, socio economic characteristics and pricing scenarios. According to pricing scenarios, 4 choices including using personal car, public transportation, taxi and cancelling the trip were presented to users which they should choose only one option due to every pricing scenario. The reliability of questionnaires have been investigated with cronbach's alpha which results showed the proper reliability of questionnaires. More than 3500 interviews were performed and after preliminary validation, were entered in the database. Based on this data, more than 70 variables were defined which their correlation was estimated and proper variables were chosen. For modeling, due to discrete nature of data, multinomial logit model was applied and calibrated for every choice. In this regard, the feasibility of applying nested logit model was also tested which results showed the invalidity of this model. More than 200 models have been calibrated and finally best validated models have been chosen for describing the mode choice of every alternative.
Results of modeling showed that having more expansive cars will increase the utility of using personal cars and reduce the public transport utilization. Also the residence location of the users is effective in their mode choice. Living in restricted zone, increase the willingness of users to use transit and paratransit mode. Users' education is also important in their choice. People with higher education level have more willingness to pay. The sensitivity analysis showed that pricing can be a proper tool for managing personal vehicles demand. When entrance toll is equal to 3000 tomans, only 35 percents use their personal vehicles. In this condition, 30 percents of users choose transit mode. Results also showed that choosing transit and paratransit mode is similar. When the toll is more than 17000 tomans, the rate of using taxi have higher growth comparing to transit utilization. Also, results showed that the demand for entering to restricted zone can be assumed inelastic. In highest toll, only 10 percents of users cancelled their trip. Finally, the sensitivity analysis for every mode has been accomplished and multiple future researches have been proposed.
Keywords: Mode Split models, Congestion pricing, stated preference method
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Numerical analysis of electrokinetic soil remediation for Mercury removal
149
158
FA
maryam
pam
student
Electrokinetic soil remediation is a promising technology that can be used for insitu treatment of fine-grained soils. In this study the numerical analyses of electro kinetic process in soil is considered. Numerical model is formulated for simulating mercury transport under an electric field using one-dimensional convection-diffusion equation that describes contaminant transport. The presented model is used for demonstrating the pH changes and mercury removal from kaolinite clay at last day. The finite difference method is used for solving the model. Computational programs were written in two ways of FTCS and Crank-Nicolson using MATLAB software. The Crank-Nicolson scheme has been more consistent with experimental results. Experimental results are used for the calibration of the model. The proposed numerical model shows good agreement with experimental results.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
APPLICATION OF SHEAR-FRICTION HINGE CONNECTION IN MID-STORY STAIR SLABS TO COLUMN JOINT
159
169
FA
Hamid Reza
Farshchi
Researcher, International Institute of Earthquake Engineering
Reinforced concrete buildings are considered as one of the most important types of structures. According to the implementation nature of these buildings, mainly as in place construction, usually their connections are performed as fixed connections. Because of restraint form of girder-column connection in the reinforced concrete buildings, their participation in the lateral load bearing will be in the form of moment frame system. Nowadays stair -column connection in the middle of story is considered as one of the design and implementation problems. Since using of multiple arm stairs is the best method in terms of performance, cost and safety to make an appropriate connection between stories, different methods will be used to transfer landing plate (stations) load to structural members in order to increase stability and safety of the stairs. Two general methods of landing plate load transfer include: A) transfer of stations load to lower or upper balanced beam of the floor B) transfer of stations load to columns around the stair. In our country more attention is paid to the second method (B) due to the ease of implementation and financial and time savings. Fixed and unchangeable behavior of landing plate- column connections in the middle of story is one of the most important properties of a good connection. This target can be achieved largely through designing and implementing of joint connections of landing plates to columns.
It is a long time that this connection is designed in our country as joint connection but there are no appropriate details of implementation for the given assumptions. Always in the typical methods there is a considerable moment imposed on the column because of restraint nature of in place reinforced concrete practice. It is clear that this unusual beam – column connection in the middle of story is considered practically an obvious weakness for these columns and the whole structure in terms of loading and final variable behaviors of several columns connected to half-height slab of the stairs. Purpose of the present study is to introduce a new joint connection that is consistent with national building regulations, part 9 and also can be easily performed and designed. Suggested connection with a shear – friction function can be applied in the connection of slab stairs in the middle of the story to columns. It can also be considered as a suitable method for consistent relationship of design and implementation.
Force transmission in this connection is just in a shear form (because moment arm is not formed) and mainly takes place by reinforcement bars. Although concrete connection friction can transmit substantial shear force; it is recommended to ignore this capacity. However, friction connection capacity is predictable and applicable in the theoretical relationships. Implementation of this connection is very simple and can be created just by preparation of several bars as antennae (dowel) with appropriate and minimum aanchorage length. Implementation of suggested connection leads to removal of the beam in the middle of the story staircase. Finally, it causes high amount of savings in the use of concrete, bars and shuttering and increases the accuracy and speed of implementation. According to loading of each staircase, amount of required reinforcement will be calculated based on shear force as well as tensile force.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Elastoplastic analysis of the tunnel considering the nonlinear variations of the strength parameters from peak to residual in the strain softening stage
171
178
FA
elahe
mohammadi
The ground response curve, (GRC), is one of the three important components of convergence- confinement method. In fact, this curve is obtained from elastic-plastic analysis of circular tunnel, which is various depending on the type of rock around an excavation, mechanical, geometrical features of it. Tunnel geometry, in situ stress, support pressure, intact rock features and fractured rock mass features, are among the effective factors on the ground response curve. Elastic-plastic analysis of a circular opening subjected to hydrostatic far-field stress has been one of the most fundamental problems related behavior of tunnels. The results of such analysis can be shown in the ground response curve. In this curve, the ratio of radial convergence of tunnel to inner pressure of tunnel is presented by with distance from tunnel face scale. This analysis can be expressed in this way relation between the convergence of the tunnel wall and radius of plastic zone around the tunnel. In this paper is presented a relatively simple procedure for the ground response curve of the circular tunnels excavated in strain softening behaviors, compatible with a nonlinear Hook-Brown yield criterion. In order to construct true GRC, it is necessary to think about the selection of the behavior parameters of rock mass and its yield criterion and analyses different states. Material with elastic-plastic behavior according to behavior after fracture are divisible to three groups including perfect plastic, perfect brittle and strain-softening. Based on the reviewed the present studies, strain-softening model is closer to behavior reality of rock masses, but the convincing methods for recognition of rocks with strain-softening behavior, has not been presented up to now. The main reason of this deficiency is the complexity of analysis of rock mass with strain-softening behavior. Lack of closed form solution for determining the relation between convergence of tunnel and inner pressure, add sth. to this problem. Most researchers, for investigation of strain-softening behavior of materials, have considered the change of the strength parameters from peak to residual in the strain softening zone as a linear function. Therefore in this article, in order to more precisely investigate the strain softening behavior, these variations are nonlinearly modeled. Therefore, dilation and friction angle parameters and the constants of the yield criterion are variable from the peak to the residual. In order to show the applicability and accuracy of the proposed procedure and investigate the effect of it in plastic region, some illustrative examples are presented here. First, the effect of different definitions for the softening parameter η is discussed by means of elasto-plastic analysis of a circular tunnel using Park, 2007 data . Second, the effect of variation of critical softening parameters on the displacement of a circular tunnel is examined by the proposed method using Carranza-Torres, 2004 data. Then the effect of different definitions for strength parameters from peak to residual, in the softening zone is evaluated by constructing the ground response curves for Park, 2007 data.
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
14
4
2015
2
1
Static analysis of urban single tunnels in alluvial using discrete element method (DEM)
179
188
FA
ehsan
manafi
Construction of urban tunnels (metro and transportation) is an integral part of the infrastructure of modern urban. Most of urban tunnels are located in alluvium. Major problem in construction of urban tunnels is settlement at the ground surface and its influence on buildings together the control of deformations around excavation area. Therefore, the accurate prediction of deformations is an important factor in tunnels projects. Because of the discontinuum nature of soils, its modeling using conventional FEM based on continuum mechanics is not completely real. Hence, in this research, considering alluvium as discrete particles, the effects of tunnel parameters such as diameter, depth and shape (construction method) on the ground deformations is examined using DEM (Discrete Element Method). For this concern, using software PFC2D based on DEM, the static analysis of circular tunnels is done. The results of DEM are compared with respect to the FEM, field data and analytical results. The comparison shows the results of DEM are more accurate than FEM especially in shallow depths and it can model the surcharge effect of tunnel smoothly.