per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
1
14
article
Seismic Demand and Capacity of Steel Moment Resisting
Frames Under Near-Fault Earthquakes Using Incremental
Dynamic Analysis
S.I. Barakati1
1
F. Daneshjoo
2
Tarbiat Modares University
Tarbiat Modares University
In seismic performance based design procedures, nonlinear static pushover analysis (SPO) and incremental dynamic analysis (IDA) are usually used for determining seismic demand and capacity of moment resisting frames (SMR). The results of these methods are often presented using curves of intensity measures (IM) Vs damage indexes (DI). For far field earthquakes, different intensity measures, such as acceleration spectral intensity of the first mode of vibration with 5% damping i.e. Sa (T1, %5) factor are used. But for near field earthquakes, it is necessary to consider other suitable IM's. In this article, the difference between IDA and SPO curves for near field earthquakes compared to that for far field earthquakes are shown for three SMR frames which are designed according to Iranian code of practice using 15 pairs of near and far field earthquakes. Then some other intensity measure factors which may be suitable for near and far field earthquakes, are considered. These IM's are compared with the use of standard definitions of "efficiency" and "sufficiency". It is concluded that intensity measure IM1I&2E which considers second mode effects and nonlinear behavior, is much more efficient and better sufficient than more often used Sa(T1, %5) factor.
http://journals.modares.ac.ir/browse.php?a_code=A-10-15255-1&slc_lang=en&sid=16
Near and far field earthquakes
Intensity measures
Nonlinear static pushover
analysis
Incremental dynamic analysis
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
15
28
article
Investigation on the Quality of Groundwater Resources of
South of Birjand Plain Using Mass Balance Techniques
B. Dahrazma
1
S.M. Mousavi
2
Shahrood University of Technology
Shahrood University of Technology
Groundwater is of important drinking water resources. The quality of those water resources which are not affected by human activities, is characterized by local geological conditions. The present research was conducted in order to investigate the quality of water resources located in the south of Birjand plain, South Khorasan Province, using mass balance techniques. This research dealt with the quality assessment and the distribution pattern of physico-chemical parameters (anions and cations, pH, EC, TSS, TDS, and TH) in the groundwater resources in the region resulting in indentifying the contamination resources. Also, the origins of anions and cations in the groundwater resources as well as their connection with the geological characteristics of the region were evaluated by employing the mass balance techniques. The water sampling was performed systematically based on the distribution wells over the plain, with regard to the distances, and perpendicular to the topographical lines from the heights toward the lower plains down to the main river, 3 kilometers apart across the plain. In average, one third of whole wells in the study area were selected for sampling. The samples were taken during the end of dry season (October 2010) from 27 wells, 2 Qanats, and 1 spring. The cations (Na +, Ca+2, Mg+2, and K+), anions (HCO- 3 , SO 4 2- , CO 3 2- , and Cl-), TSS, TDS, pH, and the total hardness of the water samples were measured in the Water, Soil, and Plant Laboratory, Kavosh Ab Shargh Khorasan Jonobi Engineering Services Co. To assess the quality of the water resources in the region, in this research the physicchemical properties of water samples were compared with ISIRI 1053 to identify the contaminated wells. The hardness of the samples was measured and the water resources types were identified using Piper Diagram. Also, through calculating the correlation factors and mass balance, hydrogeochemistry of water resources and probable origin of cations and anions were assessed. The results showed that 50%, 30%, and 10% of the groundwater resources are contaminated with magnesium, sodium, and chloride respectively. The petrological studies verified the presence of ophiolite sequence. A set of ultramafic rocks and basic magma (spilites) with wide developments in southern heights of Birjand plain which had the most effects on the water quality of the region. The water resources contaminations in the region may be due to the presence of listonites from the alteration of ultramafic rocks existed in highlands, upstream of the groundwater resources. 96% of groundwater resources are classified as very hard water. The types of groundwater vary from carbonated calcic in highlands to chloride sodic in downstream and east of the region due to high solubility of Na + and Cl- existing in the soil. %36.6 of water resources were chloric-sodic and the rest were classified as chloric-magnesic, bicarbonatesodic, and bicarbonate-magnesic. The correlation analysis of the parameters indicated that sodium has a very high correlation with chloride, potassium, and sulfate. The positive correlation of Mg 2+ with Ca2+ (+0.614) is an indication of the same origin for both ions. Also, EC with TH (+0.710) and Ca 2+ (+0.710) and TH with TSS (+0.641) show positive correlation. In general, these positive correlations indicate the common geogenic origin of cations and anions in water resources of the region. WATEVAL software was employed for calculating the mass balance using the concentration of anions and cations to find the effective parameters and origin of ions in the water resources. These calculations verify and emphasize on the influence of geological conditions of the region on hydrogeochemical properties of water resources of the plain. Mass balance analysis denotes that the origin of sodium and potassium could be the ion exchange process originated from weathering of mafic rocks (spilites) while the calcium may be released due to weathering of plagioclases of sub-volcanic mass, ferromagnesian minerals, carbonated listonite, and dissolution of limestone in the region.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-6590&slc_lang=en&sid=16
groundwater quality
Contamination
mass balance
south of Birjand plain
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
29
48
article
An investigation on Effects of Bed Permeability on
Characteristics of Turbulent Flow in Various Porosities
M. Shafieefar
1
M. Adjami
2
S.A.A. Salehi Neyshabouri
3
Tarbiat Modares University
Shahrood University, Shahrood
Tarbiat Modares University
Abstract: The two main characteristics of a porous bed are the bed material diameter – representing its coarseness - and the porosity which represents its permeability. In this paper the effect of bed permeability on the average structure of flow turbulence is investigated. Flow is modeled using an innovativecontinuum approach based on Volume Averaged Navier-Stokes Equations in several different channel bed porosities. Results of four different simulations with various porosities are presented. Bed permeability can be represented by the permeability Reynolds number, Rek, which is the ratio of effective diameter of porosity and the length scale of eddies near the bed. The Reynolds permeability number (Rek) is the best expression for the bed permeability quantity. In small Rekthe bed acts as a solid/rigid boundary and in large Rek, the bed will behave as a high permeable boundary with negligible viscosity effects. Under these conditions, the turbulence eddies along the flow are rarely observable. The reasons can be due to: 1) the mechanism of free turbulence transfer through permeable layer and/or 2) a considerable decrease in the average shear stress due to no wall-blocking and low-viscosity effects. The dominant characteristic of turbulence near a high permeable bed is relatively large eddy structures, probably originating from so-called Kelvin-Helmholtz instabilities. Suchflow pattern with large vortexes leads to high momentum exchange between the free channel flow and the two-phase flow in porous media below permeable bed. This process also increases the friction between flow and the substrate and therefore will result in moving the Logarithmic-low region slightly downward. In addition, it is observed that the log-low cur near a high permeable bed is 4% steeper than in solid and rough bed.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-985&slc_lang=en&sid=16
Continuum approach
Permeable bed
Porosity
Average flow
Navier-Stokes
equations
turbulence flow
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
49
62
article
Story Shear and Story Drift Determination of Thin Steel Plate
Shear Walls with Hinge Beam to Column Connections under
Far and Near Fault Earthquakes
M. Gholhaki
1
M. Gerami
2
A . Mahdipour
3
Semnan University
Semnan University
Semnan University
Abstract: Regard to investigations that are done about destructive earthquakes contemporarily and by contemplating on effects of different earthquakes on various types of structural systems and by recording acceleration of ground motions , researchers detected different effects of destruction in range about 15 to 60 kilometers far from epicenter of earthquake that is nominated as near fault earthquakes. the subsequences of researches which have been done in this field shows that mapping near to the fault have less effective time than mapping which are far from the fault and have one or more special pulse with a large domain and with medium to large frequency which causes to increase the domain of response spectrum in the zone of large period. and applying huge energy in short time and Sudden intense pulse in the beginning of near fault timehistories causes increasing the demand of rotational ductility in some stories and joints. In this article Regard to reliability of steel plate shear walls in recent four decades and also the fact that these structural systems have appropriate ductility to control displacements, height energy dissipation and ductile failure mechanism, the dynamic behavior of these systems is investigated .Four finite element models of 3,7,15 and 25 story buildings that used steel thin plate shear wall with hinge beam to column connections as resistant systems has created and analyzed through nonlinear dynamic analysis in ABAQUS finite element software and then response of structures such as story shear and drift angles of stories were detected. Results postulate the effects of shear distribution in near fault and regard to these purposes it seems that this fact is caused of effects of higher modes in far fault earthquakes. This situation cause of the fact that the frequency containers of near fault earthquakes are higher in range of height periods .besides Response of structures such as damage index and base shear, show that in tall steel plate shear walls (T>0.7s) effect of near fault movements on response parameters are more than those in the far fault zone. It also can be seen that base shear of the structures in far fault earthquakes fluctuates in more extended range compared to which happens in near fault structures and in near fault earthquakes base shear of most time histories don’t have much differences but in far fault earthquakes differences are relatively much. By increasing the height of SPSW’s differences between displacements in near fault and far fault earthquakes ascends. Maximum of differences between near fault and far fault responses appear in boundary of 40% to 60% of height of walls. Eventually can be said that not only higher PGA of most near fault earthquakes is a distinctive attribute in accordance with far fault earthquakes, but also higher frequency container in long period range would be devastating, regardless to higher PGA of these earthquakes.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-1201&slc_lang=en&sid=16
Thin Steel Plate Shear Wall
Hinge connection
Near Fault Earthquake
Nonlinear
Dynamic Analysis
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
63
72
article
Decreasing computational effort in structural optimization
using a multifidelity metamodel
Y. Gholipour1
1
M.M. Shahbazi
2
University of Tehran
Civil Engineering of Elm-O-Sanat University
Abstract: High fidelity models are becoming increasingly common in engineering optimization. The computation burden is often caused by expensive analysis and simulation processes in order to reach a comparable level of accuracy as physical testing data. The metamodels are initially developed as surrogates of the expensive simulation process in order to improve the overall computation efficiency. This work presents a new multilevel optimization approach for multidisciplinary structural design optimization based on multi fidelity modeling to decrease computational effort. Such method is a composition of a statistical estimating method and a metaheuristic algorithm. A low fidelity analysis response determines if the high fidelity analysis should be done or not. As a result, most of unnecessary high fidelity calculation will be omitted. The empirical results show the new algorithm causes a significant decrease in computational load as well as increase in convergence rate. Keywords: Multi level optimization; Metamodeling; Harmony search algorithm; Inverse distance weighting model.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-7219&slc_lang=en&sid=16
Multi level optimization
Metamodeling
harmony search algorithm
Inverse
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
73
84
article
Seismic design of SMRF structures using different load
patterns and their comparison with the optimum design
R . Karami Mohammadi
1
A.H. Sharghi
2
K. N. Toosi University of Technology
K. N. Toosi University of Technology
Currently, seismic design provisions of most building codes are based on strength or force (base shear) considerations. These building codes are generally regarding the seismic effects as equivalent static forces with a height wise distribution which is consistent with the first vibration mode shape. However, the design basis is being shifted from strength to deformation in modern performance-based design codes. This paper presents a practical method for optimization of steel moment resisting frames (SMRF), based on the concept of uniform deformation theory. This theory is based on this concept that the structural weight of a lateral load resisting system with uniformly distributed ductility demand-to-capacity ratio (or any other damage index) will be minimal compared to the weight of an ordinary designed system in which deformation is not distributed uniformly and just some of structural elements have reached their ultimate states. The state of uniform deformation can be achieved by gradually shifting inefficient material from strong parts of the structure to the weak areas. In the first part of this paper, the uniform deformation theory is implemented on 3, 5 and 10 story moment resisting frames subjected to 12 earthquake records representing the design spectrum of ASCE/SEI 7-10. This includes design of an initial structure according to conventional elastic design procedures, followed by an iterative assessment process using nonlinear dynamic analyses till the state of uniform deformation is achieved. Results show that the application of uniform deformation theory leads to a structure with a rather uniform inter-story drift distribution. Subsequently, the optimum strength-distribution patterns corresponding to these excitations are determined, and compared to four other loading patterns. Since the optimized frames have uniform distribution of deformation, they undergo less damage in comparison with code-based designed structures. Also, as the shear strength of each story is in proportion to the weight of that story, the optimized structures have minimum structural weight. For further investigation, the 10 story SMRF is redesigned using four existing load patterns and subjected to 12 earthquake excitations. Then a comparison is made between maximum beam rotations of each model and those belonging to the optimized one which revealed that the optimized SMRF behaves generally better than those designed by other loading patterns. Also, it is found that for none of the conventionally designed SMRFs, beam rotation demand is distributed uniformly. In other words, for all of the considered load patterns the maximum rotation of the beams in some stories exceeds the rotation associated with the performance level. Finally, assuming that the probability distribution of maximum rotations under different excitations follows a lognormal distribution, the probability of exceeding the allowable rotation associated with the LS performance level is calculated for different load patterns and compared to each other. Based on this comparison, the efficiency of each loading pattern is evaluated and the best one is determined. Application of optimization method presented in this paper avoids the concentration of deformation and damage in just one story and makes each story deformation and damage uniform over the height of the structure.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-1479&slc_lang=en&sid=16
performance-based design
Structural optimization
Uniform Deformation
Theory
Seismic Loading Pattern
nonlinear dynamic analysis
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
85
98
article
Numerical model of cone penetration determinate difference
in cohesive soil:
A. Golshani
1
R. Nemati
2
University of Tarbiat Modares
University of Tarbiat Modares
The cone-penetration test (CPT) is a well-established in situ test in geotechnical engineering for soil classification and estimation of soil properties. In a CPT, a cone shaped penetrometer is pushed into the ground at a constant rate. The resistance on the cone tip is measured and is then related to soil classification and soil properties. In this research, the finite difference analysis of large deformations for the cone penetration testing (CPT) in the cohesive soil have been conducted using FLAC 2D Software. In this modeling, interface elements between penetrometer and soil are considered and it is assumed that the penetrometer materials show rigid behavior in reaction to the soil materials. FLAC provides interfaces that are characterized by Coulomb sliding and/or tensile separation. Interfaces have the properties of friction, cohesion, dilation, normal and shear stiffness, and tensile strength there is an in-situ state of stress in the ground, before any excavation or construction is started. In FLAC 2D, an attempt is made to reproduce this in-situ state by setting initial conditions. Ideally, information about the initial state comes from field measurements. Boundary conditions are modeled as axesymmetry. Horizontal and vertical direction at the bottom boundary and horizontal direction at the vertical boundary of soil model are fixed. Soil behavior follows full elastic–plastic model and Mohr-Coulomb failure criterion. Numerical model is analyzed to achieve mesh convergency at the various grids. The values of cone and frictional resistance have been obtained through software calculations and then compared with the results obtained from cone penetration test at the aluminum melt factory in Lamard, Fars Province. Stress and displacement contours are related for evaluation of the penetration process. Steady state is considered to achieve steady stress range in which the hole diameter is equal with the CPT hole. The numerical modeling results of CPT test by FLAC 2D software shows good agreement with the field tests results. Furthermore, the results have been discussed by using Robertson Chart 1986 and Eslami- Felonious Chart 1997. Charts almost show same profile with the field test results at the aluminum melt factory site.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-5534&slc_lang=en&sid=16
finite difference analysis
Cone penetration
Cone resistance
Interface element
Mesh Convergency
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
95
104
article
Modeling the Saltation and Evaluating the Parameters Affecting the Random Movement of Sediment Particles in Bed Load Transport Under Steady Flow
S. Kaboorani
1
, A. Shanehsazzadeh
2
TarbiatModares University
University of Isfahan
Study on the physics of sediment particle movement at grain scale is essential for better understanding sediment transport phenomenon and estimating the rate of sediment transport in rivers and marine environment. Sediment particles basically transport in two modes of bed and suspended load. Bed load takes place through sliding, rolling and saltation, from which the latter is dominant. Many parameters influence on saltation phenomenon, which their effects are not fully understood. These influencing parameters make the saltation a stochastic phenomenon. In the present article the influence of the affecting parameters on movement of sediment particles at saltation mode of transport under unidirectional steady flow are investigated. A numerical model is developed to simulate the particle motion in bed load saltation with considering the main contributor forces. Then the influencing parameters that effect on the jump length and average velocity of the particles are studied. Among them are the initial condition, the particle position between other particles and the shape of particles. The influence of the velocity profile on the jump length and average velocity of the particles are also studied. In summary, the change in the initial condition including the initial velocity and angle produces less than 10% variation on the particle jump length and velocity. On the other hand the position of the grain between the other particles is considerably influential with 40% change in the jump length and average velocity. The particle shape is most important parameter in term of the influence on the jump length and average velocity; there is a 50% difference between the jump length of spherical particles and flake-shape particles, for average velocity it is about 10%. The result of the study improves our understanding of particle motion at grain scale and ultimately results in the better estimation of sediment transport rate.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-7205&slc_lang=en&sid=16
sediment transport
bed load
steady flow
saltation
Numerical Modeling
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
99
108
article
Study the Influences of Nano-Silica on Electrical Resistivity
of Cement Paste
M. Maghrebi
1
M. Khanzadi
2
M. Habibian
3
M. Tadayon
4
University of Science and Technology
University of Science and Technology
Buali Sina University of Hamadan
This paper presents the influences of adding nano-silica on electrical resistivity of cement paste, because the electrical resistivity test is one of the non-destructive test in durability issues that can help us to assess the resistance of cement is facing by ion attacks. Furthermore, because the transition area in concrete is one the weak parts of concrete. It is tried to improve the durability properties of transition area that is mainly filled by cement and water. So, this research focuses on assessing the electrical resistivity of cement paste when it is integrated with pozzolan material in nano and micro scale. In to end, the cement paste without any additive is compared with cement paste integrated with nano-silica and micro silica. The amounts of additive materials are limited to 2.5%, 5%, 7.5% and 10% of cement weight. The two types of nano-silica have been used in this research that are liquid suspended nano-silica and solid nano-silica particle. So, the 3 different pozzolan materials were used that include two different nano silica (liquid and solid) and micros silica. Then all the results have been compared with results of ordinary cement paste as reference point. Then the samples were tested at age of 3, 28 and 90 days. The results show that before age of 3 days, adding nano silica or micro silica led to decline the electrical resistivity because the pozzolanic reaction is not started, but at age of 28 days the top achieved electrical resistivity belong to the samples which has nano-silica in its mixture. However, after age of 28 days, just the samples with micro-silica have electrical resistivity growth. The results of the samples that contain the both of nano-silica and micro-silica are between the results of samples that contain micro-silica and the samples which integrated by nano-silica. Keywords:
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-5623&slc_lang=en&sid=16
Nano-silica
Electrical Resistivity
Micro-Silica- pozzolan
Cement paste
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
109
119
article
Aberrant Driving Behavior of Iranian Drivers:
An Internet-Based Survey
A.R Mamdoohi
1
A. Mohammadi Hazaveh
2
M. Fallah Zavareh
3
Tarbiat Modares Uni
Tarbiat Modares University
Tarbiat Modares University
Road crashes cause more than 20 thousand fatalities each year in Iran. Human factors consisting of driving styles and skills have been recognized as important contribiuting factors in most traffic crashes. Focous on driving behavior has been the subject of many researches. Driver Behavior Questionnaire (DBQ) in this regard is a relatively new, important and widely used instrument, devised to identify the components of the structure of aberrant driving behaviors. Surveys based on DBQ, urges respondents to self-report the frequency of aberrant driving behaviors during a specific period of time. Investigation of driving styles is estimated to be the subject of more than 170 researches since DBQ was first by Reason et al in the 90’s. Since then, many researchers have employed the original DBQ or a modified version, either to explore behavioral components (exploratory approach) or to confirm a given setting based on authors’ theories or observations, in group(s) under the study (confirmatory approach). Lack of exploratory analysis and spatial dispersion of respondents in the previous domestic researches, motivated the authors of this paper to conduct a new survey to investigate aberrant driving behaviors among Iranian drivers applying exploratory approach. The original DBQ was modified, validated and dispersed between Iranian drivers through an internet-based survey. Recent increase in the number of internet users in Iran, more interactions between respondants and the questionnaires, the power of self-administration, massive reductions in cost and time over interviewer-administered surveys, building a database, were among factors yielding hope that the sample would be comprehensive enough to comprise different groups of drivers. Using social networks and email services, the proposed questionnaire was exposed to internet users and a sample of 213 drivers (165 males and 48 females) from 40 cities inside and outside Iran, filled out the 37-item DBQ. Principal Component Analysis (PCA), with Varimax Rotation implied, a five-factor structure: “Push and Speed Violations”, “Disregarding the Regulations”, “Lack of Concentration while driving”, “Aggressive Violation” and “Lapses and Error” for Iranian drivers. These components account for 42.2 percent of the total variance. It is worth noting that the distinction between different kinds of violation and lapses and error support the fact that this new structure is consistent with the previous studies. Moreover, using cell phone while driving (both sending texts and talking), aggressive violations and push and speed violations are the most frequent aberrant driving behaviors. Compared to the other countries, drivers in Iran reported more violations than drivers in industrialized countries and fewer violations than Asian drivers. Results also show that unlike industrialized countries, Iranian drivers reported more aggressive violations than ordinary violations.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-1373&slc_lang=en&sid=16
Aberrant driving
Driver Behavior Questionnaire
Internet-Based Survey
Principal component analysis
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
121
133
article
Simulation of Anisotropy in Soft Rock
Using a Multilaminate Model
R. Mahin Roosta
1
N. Jaafari
2
Mahab Ghodss Consulting Engineering Co
Zanjan University
Due to sedimentation process, structure of particles and subsequent loading history, most of the natural soil and rock deposits, tend to be highly anisotropic, which manifests itself in the directional dependence of deformation and strength characteristics. Also, existence of discontinuities such as joints and faults cause anisotropic behavior in the rock mass. Different constitutive models have been introduced by researchers to simulate the inherited or induced anisotropy in geo-materials. Due to the concept of the multi-laminate framework, in which yield and plastic potential functions are defined on a number of independent acting planes, plastic flow is developed independently on different planes. Therefore multi-laminate models are able to simulate induced anisotropy, intrinsically. In this study, a constitutive model based on multi-laminate framework with Mohr-Coulomb failure criterion for modeling the anisotropy is written and added to a two-dimensional explicit finite difference program, FLAC. In this model, anisotropy of geo-materials can be modeled in tow different ways; the first way is used to model jointed rocks with the assumption that a pronounced anisotropy of rock can be described by introducing a certain number of planes of weakness and behavior of rock mass can be determined from interaction of the joint planes and the intact rock. In the second way, anisotropy of sedimentary materials can be introduced in a straightforward manner by varying model parameters over the sampling planes that obtains by the parameters in the vertical and horizontal direction. When the number of plans is less than 5, geo-material is considered as the jointed rock mass with those number of joint sets, otherwise, geo-material considered as the sedimentary rock or soil mass; so application of different yield strength in numerous contact plane with uniform distribution, enable the model to simulate anisotropy in intact samples. For each contact plane, two failure criteria are considered associated with two potential functions. In fact non-associated flow rule and associated flow rule are applied to simulate plasticity formulations in shear and tensile mode of failure, respectively. Strength parameters of each contact plane are calculated based on its dip angle and the strengths of the intact soft rock in the direction of parallel and vertical to the sedimentation. The capability of the model is demonstrated by numerical simulation of uni-axial tests on jointed rock mass and the results are compared with those from analytical closed form solutions. The effect of anisotropy in friction angle and cohesion are investigated through the model in order to present sensitivity of the model to anisotropy ratio and angle of sedimentation. Finally the proposed model is used to simulate stability of a slope in the sedimentary domain; the results show that with a constant sedimentation angle, increase in anisotropy ratio will increase the differences of the safety factor of the slopes with isotropic and anisotropic behavior.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-6343&slc_lang=en&sid=16
Anisotropy
Shear Strength
Multi-Laminate Model
Joint
Sedimentary soft rock
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
135
145
article
Experimental Investigation of Scour Hole Length and
Reynolds number variations under Different
Bank Slopes in Rivers
F. Noorbalhsh
1
M.R. Majdzadeh Tabatabai
2
M.H. Kharazifard
3
Power and Water University of Technology
Shahid Beheshti University
Shahid Beheshti University
River bank erosion causes damages to agricultural land, adjacent establishments and widening of river dimensions. Mass failure process of bank erosion is a factor to transport bulk of sediments followed by deposition in downstreams of a river system, which could be an important problem in river management. This research is to investigate internal erosion under different bank and floodplain slopes, By this means, a number of experiments were carried out in a model designed to simulate internal river bank erosion in the laboratory. In these experiments, the scour hole length, resulted from internal erosion and seepage discharge were measured under different hydraulic gradients. Results showed that bank slope plays an effective role in scour hole length and calculated Reynolds number in porous medium. As it was observed that the scour hole length and hydraulic gradient decrease with an increase in the bank slope and porous medium Reynolds number decreases with reduction in the hydraulic gradient.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-1213&slc_lang=en&sid=16
Internal erosion
Rivers Bank slope
Scour hole length
Reynolds number
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
147
157
article
Influence of Temperature on Unconfined Compressive
Strength and Water Absorption of Sand-Bentonite Mixture in
the Presence of Carbonate
V.R. Ouhadi
1
M. PourZafarani
2
Bu-Ali Sina University, Hamedan
Bu-Ali Sina University
influenced by temperature. On the other hands, the existing of carbonate as one of the major components of clayey soils in arid and semi-arid lands, and its effect on engineering properties of the soils prove the necessity to study the simultaneous influence of carbonate and temperature on the engineering behavior of clayey soils. In the present work, the interaction between clay and carbonate in high temperatures has been investigated. Bentonite were mixed with different percentages of carbonate and sand. The variations of added carbonate were 0% (natural carbonate content), 10%, 20%, and 30%, respectively, and added sand were 20% and 40%. The soil samples were carefully mixed with enough water to bring them to their plastic limit and were kept in plastic bag for uniform-moisture distribution for a period of 24 h. It was then sieved through a #10 mesh to ensure to achieve a uniform mixture. Samples for testing were then prepared by compacting soil mixtures into cylinder mold in three layers. The test specimen dimensions were 35 mm in diameter and 70 mm in height. The clay specimens were allowed to air dry at room temperature for 24 h. Bentonite specimens were kept in plastic bag to prevent development of cracks during air drying due to high crack potential. The samples were then oven dried at 110 °C for a period of 24 h. The test specimens were heated to temperatures of 300, 500, 700, 900 and 1100 °C, using programmable Carbolite electric furnace. The specimens were placed in the electric furnace at room temperature and then the temperature was increased at a rate of 3 °C/min until the desired temperature was reached. Once the treatment temperature was reached, it was held at that stage for 2 h, then the furnace was turned off. The specimens were then allowed to cool overnight in the closed furnace. After this curing condition, samples with different levels of temperature including 25 °C (laboratory temperature), 110, 300, 500, 700, 900 and 1100 °C were used for experiments. The changes of physical and engineering properties of the soil were studied by performing macro-structural tests such as linear shrinkage, water absorption and unconfined compression. The results show that as temperature increases close to the de-hydroxylation temperature, strength gradually increases. At de-hydroxylation temperature, the strength significantly increases, so that the strength of bentonite specimens increases 3 to 4 times. The strength of bentonite specimens significantly decreased with increasing the heat over de-hydroxylation temperature. This strength reduction was due to the formation of microscopic voids and pores in the specimen. Analyzing the simultaneous influence of carbonate percentage and heating indicate that the increase of carbonate percentage in a given temperature results in the decrease of strength and the amount of this reduction is different in different temperatures. In bentonite specimens, heating causes the water absorption to be decreased, however, the increase of carbonate percentage results in the increase of water absorption in a given temperature. Temperature, Bentonite, Calcium carbonate, water absorption, Unconfined compressive strength.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-1776&slc_lang=en&sid=16
temperature
Bentonite
Calcium carbonate
Water Absorption
Unconfined
compressive strength
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
159
167
article
Optimization of Reactive Blue 19 adsorption from aqueous
solution by pomegranate residual-based activated carbon
using Taguchi method
E. Radaei
1
M.R. Alavi Moghaddam
2
M. Arami
3
Amirkabir University of Technology
Amirkabir University
Amirkabir University
Dyes are being extensively used in textile, dyeing and leather industries and usually have a synthetic origin and complex chemical structure that may be mutagenic and carcinogenic. Among various processes of dye removal from wastewater, adsorption is considered to be the most efficient process. Activated carbon is the most widely used adsorbent with great success because of its high adsorption capacity, but its use is limited due to its high-cost, has led to a search for cheaper substitutes. Optimization methods, such as the Taguchi method has been generally adopted to optimize the design parameters, because this systematic approach can significantly minimize the overall testing and the experimental costs. In this study; the optimum condition of Reactive Blue 19(RB19) removal by activated carbon based on pomegranate residual is determined using Taguchi method. For this purpose, 4 main factors such as pH, adsorbent dose, initial dye concentration and contact time were considered in 5 levels. Therefore, an L25 orthogonal array was chosen, and the experimental conditions were obtained. In addition, after design of experiments, an analysis of the signal-to-noise (S/N) ratio was needed to evaluate the experimental results. The analysis of mean (ANOM) statistical approach was adopted herein to construct the optimal conditions. In addition to ANOM, the analysis of variance (ANOVA) statistical method was also used to analyze the influence of each controllable factor on the dye removal efficiency. To prepare the To prepare the activated carbon (AC), pomegranate residual was collected. Collected sample has been dried in an oven for 2 h at 100 0C. It was then ground in a ball mill and the material passed through the No.30 mesh was collected and tested. They were soaked for 24 h in a 1:1 wt. ratio with 50 wt. % phosphoric acid as the carbonized at room temperature. The sample is then decanted and dried in a muffle furnace for 1 h at 500 0C. They were then washed sequentially several times with hot distilled water, until pH of the washing solution became neutral. AC was finally powdered and sieved by the No. 100 mesh. The experiments were done 3 times according to the tests conditions determined by the Taguchi method and the dye removal efficiency was measured. Due to the results of S/N and ANOM, it can be inferred that the optimum mixture proportions to obtain the highest RB19 removal efficiency are as follows. (1) Initial dye concentration of 100 mg/L; (2) pH of 11; (3) adsorbent dose of 1.75 gr/L; and (4) contact time of 7 minutes. The experiment with aforementioned condition was done and result was shown the highest efficiency (98.94%). According to the result of ANOVA, the rank order of the contribution percentage of each factor on RB19 removal efficiency is as follows: (1) initial dye concentration (52.67%), (2) adsorbent dose (33.32%), (3) pH (13.61%), and (4) contact time (2.72%).
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-6234&slc_lang=en&sid=16
Adsorption
Taguchi
Reactive Blue 19
pomegranate residual
Analysis of Variance
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
169
179
article
Numerical simulation of impact penetration in concrete target
and investigating of empirical solution
T. Alizadeh
1
J. Moradloo
2
J. Moradloo
3
University of Zanajan
University of Zanajan
University of Zanajan
Understanding the behavior of concrete at high strain rates loading is a critical issue for theory and applied purposes. The concrete is non-linear, rate-sensitive and pressure-dependent material that will add more difficulties in its modeling at high loading conditions such as impact penetration situations. In the present study, numerical simulation of penetration in a concrete target using an advanced plasticity concrete model is presented using explicit finite element (FE) analysis. A full 3D FE model of impact on unreinforced concrete specimens is carried out. The analysis includes initiation and progressive damage of the composite during impact and penetration Also comparison between some empirical solutions is carried out and their accuracy and precision are checked used experimental solution. Concrete nonlinear behavior was modeled using RHT model which is an advanced plasticity model for concrete at high strain rate loading condition. Two test examples are presented to demonstrate the proposed method. They involve the impact of an ogive-nose projectile on concrete cylinders with variable dimensions. The FEM computational results obtained using RHT plasticity model are very close to the test data, implying that the proposed method will be promising in studies of impact analyses of concrete structures subjected to impact loading. In using RHT model with the default model parameter values, the experimental results cannot be reproduced satisfactorily. Deduced results having good agreement withexperimental ones using suitable calibration of plasticity model parameters value. The RHT plasticity concrete model was developed as an enhancement to the JH concrete model by the introduction of several new features. In this new model, the strain hardening and the third invariant dependence were considered. An independent fracture strength surface was incorporated to allow for a more appropriate modeling of the material softening response. In addition, the concrete hydrostatic tensile strength was made rate dependent. Using a modified parameter setting, the RHT model implemented in AUTODYN hydrocode exhibits a generally excellent behavior. In this paper also, a comprehensive evaluation study of several widely used empirical penetration depth relation is presented. The model formulations are scrutinized and numerical tests are carried out to examine their actual performances subjected to various loading conditions. Comments on the limitations and the appropriate use of these models are given. In addition to penetration depth, damage extension, concrete sapling, scabbing and output velocity of missile and other time dependent structural quantities can captures well. This is in contract with imperial relations that have only penetration depth calculation capability for special conditions. On the other hand investigating of empirical relation shown in addition to their finite application ranges, they haven't good results in majority of cases. Among them, US army corps of engineers'' experimental based relation have better results compared other empirical relations for calculation of penetration depth.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-3920&slc_lang=en&sid=16
Concrete penetration
empirical relation
Numerical solution
Impact
nonlinear
solution
RHT plasticity model
per
Tarbiat Modares University
Modares Civil Engineering journal
2476-6763
2476-6763
2014-06
14
1
181
193
article
Introduction of “Modified Response Modification Factor
Method” for Structural Seismic Design
M. Mahmoudi
1
S. Javadian Fard
2
Shahid Rajaee Teacher Training University
Shahid Rajaee Teacher Training University
The traditional procedure for seismic design of building structures has been generally termed the force-based design (FBD) method. In the FBD method, the elastic seismic force acting on the structure is calculated first with the aid of a design acceleration response spectrum. This elastic force is then divided by a reduction factor called behavior factor R, representing the ductility and overstrength capacities of the structures. The implementation of FBD in seismic codes, does not clearly define the performance level. Furthermore, this method assumes the constant behavior factor values for the structures with the similar types of the lateral load resisting systems and do not take into account structure numeral properties same as the influence of the number of stories. These are some disadvantages of the FBD method that have been referred in many researches. So recently, procedures have been developed to substitute for this method. The design procedure would be more rational if the performance of the structure was quantified through a target value of deformation treated as an input variable in the design procedure. This target value of deformation can be assigned to different performance objectives and is the starting point for the development of the rather new displacement-based seismic design (DBD) method and is described in the some guidelines and publications as a performance-based seismic design method. The third and newest seismic design method is called the hybrid force/displacement-based design (HBD) method that adopts the seismic design philosophy based on both the resistance performance-based seismic design method. The third and newest seismic design method is called the hybrid force/displacement-based design (HBD) method that adopts the seismic design philosophy based on both the resistance and the performance. The HFD method combines the best elements of the FBD and DBD methods and tries to avoid those ones, which are usually thought of as disadvantages. This research proposes a new hybrid force/displacement-based seismic design method that is named the modified behavior factor (MBF) method. The MBF method combines the FBD method of the Iranian Earthquake Resistance Design Code (Standard No. 2800) and the DBD method of the Iranian Instruction for Seismic Rehabilitation of Existing Buildings (Publication No. 360). Two 5 and 7 story frames with three bays have been seismically designed by the MBF and the FBD methods and the results of them have been compared. The seismic responses of the MBF method are more precise than the responses of the FBD method.
http://journals.modares.ac.ir/browse.php?a_code=A-10-1000-3225&slc_lang=en&sid=16
Performance-based seismic design
Force-based design
Displacement-based
design
Hybrid-based design
The modified response modification factor method