en jalali 1391 9 1 gregorian 2012 12 1 10 4 online 1 fulltext

en The nonlinear static procedures (NSPs) proposed by design codes do not lead to reliable results especially for tall buildings. They generally provide inconsistent estimates of inelastic seismic demands, especially for the top floors due to their inabilities in considering the higher modes effects. In this paper, a new enhanced pushover procedure is proposed which is based on the envelope of the structural responses resulting from two separate pushover analyses as a combination rule. Also, the suggested pushover analyses are performed using a newly proposed modal load pattern, i.e., the Modal Spectra Combination (MSC), and the ASCE41-06 required first mode load pattern. The MSC load pattern is consisted of a number of mode shapes combined with appropriate weighting factors that depend on their modal participation factors, modal frequencies and design spectral values. A number of 2-D steel moment resisting frame models with different number of stories are used to investigate the efficiency of the proposed method. The inter-story drifts and the maximum plastic beam moment and curvature responses are used as a measure to compare the results obtained from the nonlinear time-history analyses (NL-THA) and some other NSPs. The results obtained through rigorous nonlinear dynamic analyses show that the application of the proposed method leads to acceptable results for steel MRF systems in comparison to other available enhanced NSPs. The OpenSees program is used for numerical analysis. Nonlinear static analysis, Pushover analysis, Lateral load pattern, Nonlinear dynamic analysis 245 252 http://ijce.iust.ac.ir/browse.php?a_code=A-10-152-1&slc_lang=en&sid=1 2011/06/13 1390/3/23 2015/10/25 1394/8/3 F.R. Rofooei Professor, Civil Engineering Department, Sharif University of Technology, Tehran, Iran rofooei@sharif.edu 0031947532846009783 0031947532846009783 Yes M. R. Mirjalili Doctoral Student, Structural Engineering, Civil Engineering Department, Sharif University of Technology, Tehran, Iran m.mirjalili@yahoo.com 0031947532846009784 0031947532846009784 No N. K. A. Attari Assistant Professor, Department of Structural Engineering, Building and Housing Research Center (BHRC), Tehran, Iran n.attari@bhrc.ac.ir 0031947532846009785 0031947532846009785 No

en Strut-and-Tie Model (STM) can be used to model the flow of compression within a concrete strut. Concrete struts are formed in various shapes such as prismatic or bottle-shaped. In order to study the behavior of concrete struts, a series of simple tests were performed. Eighteen reinforced concrete isolated struts with compressive strength of 65 MPa were tested up failure under point loading in the plane of specimens. The tested specimens were reinforced by various reinforcement layouts. The behavior of tested beams was investigated. Observations were made on transverse displacement, primary cracking and ultimate failure load and distribution of strain on the face of tested panels. Based on these observations, the geometry of the concrete struts was examined. a new model to analysis of concrete struts was proposed based on modified compression field theory (MCFT). A database of 44 tested specimens was compiled to evaluate the proposed model. The results indicate that using the ACI and CSA codes expressions regarding the amount of minimum required reinforcement in a strut produces conservative but erratic results when compared with the test data. Conversely, the new proposed model presents a more accurate prediction for the strength of 44 tested struts. Strut-and-tie, Transverse reinforcement, Strut, Efficiency factor 253 262 http://ijce.iust.ac.ir/browse.php?a_code=A-10-574-2&slc_lang=en&sid=1 2011/06/132010/09/5 1389/6/14 2015/10/252015/10/25 1394/8/3 A. Arabzadeh Associate Professor, Structural Engineering Dept., Tarbiat Modarres University, Tehran, Iran arabzade@modares.ac.ir 0031947532846009786 0031947532846009786 Yes R. Aghayari Assistant Professor, Civil Engineering Dept., Razi University,Kermanshah, Iran reza_agh@razi.ac.ir 0031947532846009787 0031947532846009787 No A. R. Rahai Professor, Faculty of Civil Engineering, Amir Kabir University of Technology, Iran Rahai@aut.ac.ir 0031947532846009788 0031947532846009788 No

en In order to lighten the prestressed concrete solid members, nowadays, it is possible to make use of the advantage of HPC (fc;#39>60 MPa) as well as replacing the solid section with a PSC thin-walled section for certain members such as circular and box columns. Using the strength theory of ACI, a numerical procedure along with a computer program was developed for the analysis of such sections subjected to axial compression or tension load and bending moments. The program solves for all possible variables such as, concrete compressive strength (fc;#39= 60-100 MPa), type of prestressed steel, concrete cover, ratio of wall thickness to the section dimensions and the PS steel arrangements to satisfy the given loading cases, thus leading to an optimal cost solution. However, since the cross section is thin-walled circular or box and the PS steel is located at discrete points along the periphery of a circle or rectangle, the equations of equilibrium are complex for hand computations (especially for circular section) but suitable for computer program. So, by use of MATLAB software the interaction diagrams were also drawn for the analysis of such sections for all mentioned variables. The use of prestressed thin-walled column diagrams is a safe and easy tool for the analysis of such columns. Finally, the accuracy of the proposed method is demonstrated by comparing its results to those of the available experimental values and is indicate that the proposed method predict very well the capacity of prestressed thin-walled column. Analysis, Prestressed HPC, Thin-walled columns, Interaction diagrams 263 273 http://ijce.iust.ac.ir/browse.php?a_code=A-10-94-1&slc_lang=en&sid=1 2011/06/132010/09/52009/11/7 1388/8/16 2015/10/252015/10/252015/10/25 1394/8/3 A. A. Maghsoudi Associate Professor, Civil Engineering at Kerman University,Kerman, Iran maghsoudi.a.a@mail.uk.ac.ir 0031947532846009789 0031947532846009789 No H. Akbarzadeh Bengar Assistant Professor, Civil Engineering at University of Mazandaran, Babolsar, Iran h_akbarzadeh_b@yahoo.com 0031947532846009790 0031947532846009790 Yes

en The main objective of this study is to drive a simple solution for prediction of steel fiber reinforced concrete (SFRC) behavior under four point bending test (FPBT). In this model all the force components at the beam section (before and after cracking) are formulated by applying these assumptions: a bilinear elastic-perfectly plastic stress-strain response for concrete behavior in compression, a linear response for the un-cracked tension region in a concrete constitutive model, and an exponential relationship for stress-crack opening in the crack region which requires two parameters.Then the moment capacity of the critical cracked section is calculated by applying these assumptions and satisfying equilibrium lawat critical cracked section. After that, parametric studies have been done on the behavior of SFRC to assess the sensitively of model. Finally the proposed model has been validated with some existing experimental tests.The result shows that the proposed solution is able to estimate the behavior of SFRC under FPBT with simplicity and proper accuracy. Steel fiber reinforced concrete, Flexure, Stress-crack opening, Four point bending test (FPBT) 274 279 http://ijce.iust.ac.ir/browse.php?a_code=A-10-91-2&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/18 1388/7/26 2015/10/252015/10/252015/10/252015/10/25 1394/8/3 R. Ahmadii PHD of Structure, Assistance Professor of BHRC (Building and House Research Centre), Tehran, Iran r_ahmadi@iust.ac.ir 0031947532846009791 0031947532846009791 No P. Ghoddousi PHD of Structure, Assistance Professor of Iranian University of Science Technology, Tehran, Iran ghoddousi@iust.ac.ir 0031947532846009792 0031947532846009792 Yes M. Sharifi PHD Candidate of Iranian University of Science Technology,Tehran, Iran Mahdysharify@Gmail.com 0031947532846009793 0031947532846009793 No

en A comparison between design codes i.e. ACI and AISC-LRFD in evaluation of flexural strength of concrete filled steel tubular columns (CFTs) is examined. For this purpose an analytical study on the response of CFTs under axial-flexural loading is carried using three-dimensional finite elements with elasto-plastic model for concrete with cracking and crushing capability and elastoplastic kinematic hardening model for steel. The accuracy of the model is verified against previous test results. The nonlinear modeling of CFT columns shows that the minimum thickness that recommended by ACI and AISC-LRFD to prevent local buckling before the steel shell yielding for CFT columns could be decreased. The comparison of analytical results and codes indicates that the accuracy of ACI method in estimation of axial-flexural strength of CFT columns is more appropriate than AISC-LRFD. The ACI lateral strength of CFTs is located on upper bond of the AISC-LRFD’s provisions. AISC-LRFD estimates the lateral strength conservatively but ACI in some ranges such as in short columns or under high axial load levels computes lateral strength in nonconservative manner. Supplementary provisions for post local buckling strength of CFT columns should be incorporated in high seismic region. This effect would be pronounced for column with high aspect ratio and short columns. Code, Concrete, Steel, Finite element modeling, Composite member, Confinement 280 290 http://ijce.iust.ac.ir/browse.php?a_code=A-10-283-1&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/182011/02/14 1389/11/25 2015/10/252015/10/252015/10/252015/10/252015/10/25 1394/8/3 B. Beheshti-Aval Associate Professor, Civil Engineering Faculty, K.N.Toosi University of Technology, Tehran, Iran beheshti@kntu.ac.ir 0031947532846009794 0031947532846009794 Yes

en The aim of current study is to investigate the effect of Carbon Fiber Reinforced Polymer (CFRP) composites on the fatigue response of reinforced concrete beams. 6 reinforced concrete (RC) beams from which 3 were retrofitted with CFRP sheets, were prepared and subjected to fatigue load cycles. To predict and trace the failure occurrence and its growth, a small notch was induced at the middle span in bottom surface of all RC specimens. At the certain points, strains in concrete and CFRP were measured in each cycle. The upper limit of applied load was considered at the level of design service load of bridges. In addition, strain measurements facilitated to the calculation of interfacial shear stresses between concrete substrate and the CFRP layer. The variation of such stresses through load cycles has been presented and discussed. Also, a discussion on possibility of the local debonding phenomenon resulted from such interfacial stresses was presented. Load–deflection curves, strain responses and propagation of tensile cracks provided an insight on the performance of the CFRP strengthened beams subjected to different cycles of fatigue loading. Variation of load-deflection curves through fatigue load cycles depicted stiffness degradation which was discussed in the research. Carbon fiber reinforced polymer, Fatigue, Interfacial shear stresses, Tensile cracks 291 300 http://ijce.iust.ac.ir/browse.php?a_code=A-10-258-1&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/182011/02/142012/01/23 1390/11/3 2015/10/252015/10/252015/10/252015/10/252015/10/252015/10/25 1394/8/3 M. Z. Kabir Associate Professor, The corresponding author, Department of Civil and Environmental Engineering, AmirKabir University of Technology, Tehran, Iran mzkabir@aut.ac.ir 0031947532846009795 0031947532846009795 Yes A. Hojatkashani PhD, Department of Civil and Environmental Engineering,AmirKabir University of Technology, Tehran, Iran ata_hojat@aut.ac.ir 0031947532846009796 0031947532846009796 No

en Barrel vaults are attractive space structures that cover large area without intermediate supports. In this paper, the charged search system (CSS) optimization algorithm is employed for optimal design of barrel vaults. This method utilizes the governing laws of Coulomb and Gauss from electrostatics and the Newtonian law of mechanics. The results demonstrate the efficiency of the discrete CSS algorithm compared to other meta-heuristic algorithms. Heuristic optimization algorithm, Charged system search, Optimal design of barrel vaults 301 308 http://ijce.iust.ac.ir/browse.php?a_code=A-10-218-56&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/182011/02/142012/01/232011/10/9 1390/7/17 2015/10/252015/10/252015/10/252015/10/252015/10/252015/10/252012/01/10 1390/10/20 A. Kaveh Iran University of Science & Technology alikaveh@iust.ac.ir 0031947532846009797 0031947532846009797 Yes M. Farahani Iran University of Science & Technology mahdifarahani84@yahoo.com 0031947532846009798 0031947532846009798 No N. Shojaei Sadra University na_shojaei85@yahoo.com 0031947532846009799 0031947532846009799 No

en Chloride ion ingress in concrete is the main reason of concrete corrosion. In real world both uncertainty and stochasticity are main attributes of almost all measurements including testing and modeling of chloride content profile in concrete. Regarding these facts new models should be able to represent at least some of the uncertainties in the predictions. In this paper after inspiration from classical physics related to diffusion and random walk concepts a stochastic partial differential equation (SPDE) of diffusion is introduced to show a more realistic modeling/calibration scheme for construction of stochastic chloride content profile in concrete. Diffusion SPDE provides a consistent quantitative way of relating uncertainty in inputs to uncertainty in outputs. Although it is possible to run sensitivity analysis to get some statistical results from deterministic models but the nature of diffusion is inherently stochastic. Brownian motion process (Wiener process) is used in SPDE to simulate the random nature of the diffusion in heterogeneous media or random fields like concrete. The proposed method can be used to calibrate/model the chloride ion profile in concrete by only some limited data for a given depth. Then the stochastic chloride ion diffusion can be simulated by langevin equation. Results of the method are compared with data from some references and all show good agreements. Concrete corrosion, Markov process, Stochastic partial differential equation (SPDE), Langevin equation 309 316 http://ijce.iust.ac.ir/browse.php?a_code=A-10-237-3&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/182011/02/142012/01/232011/10/92011/10/30 1390/8/8 2015/10/252015/10/252015/10/252015/10/252015/10/252015/10/252012/01/102015/10/25 1394/8/3 A. Tarighat Assistant Professor, PhD, Civil Engineering Department, Shahid Rajaee Teacher Training University, Shabanlou St., Lavizan, Tehran,Iran tarighat@srttu.edu 0031947532846009800 0031947532846009800 Yes

en Learning rapidly and competently has become a pre-eminent strategy for improving organizational performance in the new knowledge era. Improving dynamic learning capability is an exclusive strategy for corporate success in construction industry. Thus engineering design firms should implement OL to accomplish a state of readiness for change and develop a competence to respond and identify future business potentials. This study aims to analyze the relationship between organizational learning (OL) and performance improvement (PI) in civil engineering design firms of Turkish construction industry. OL structure in engineering design firms incorporates five constructs: organizational environment, strategy development and implementation, supportive leadership, leveraging knowledge, and learning capability. The empirical data was collected through a questionnaire survey conducted to engineering design firms registered to the Turkish Chamber of Civil Engineers. The hypothesized model relationships were tested using Structural Equation Modeling (SEM). The results show that each of the variables has a different role and significant positive impact on the OL process and organizational PI. The variables “Supportive leadership” and “Learning capability” proved to be strongly significant and positively related to organizational performance in engineering design firms. In engineering design firms, supportive leadership is needed in order to establish a participative cultural environment that helps design a new form of organization which emphasizes learning, flexibility, and rapid response. Learning capability is the potential to explore and exploit knowledge through learning flows that make possible the development, evolution and use of knowledge stocks enacting engineering design firms and their members to add value to the design business. Organizational learning, Performance improvement, Civil engineering design firms, Construction industry 317 327 http://ijce.iust.ac.ir/browse.php?a_code=A-10-431-1&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/182011/02/142012/01/232011/10/92011/10/302010/09/20 1389/6/29 2015/10/252015/10/252015/10/252015/10/252015/10/252015/10/252012/01/102015/10/252015/10/25 1394/8/3 I. Yitmen Department of Civil Engineering, European University of Lefke,Gemikonagi, Lefke, Kibris, Mersin 10 Turkey iyitmen@eul.edu.tr 0031947532846009801 0031947532846009801 Yes

en Runoff simulation is a vital issue in water resource planning and management. Various models with different levels of accuracy and precision are developed for this purpose considering various prediction time scales. In this paper, two models of IHACRES (Identification of unit Hydrographs And Component flows from Rainfall, Evaporation and Streamflow data) and ANN (Artificial Neural Network) models are developed and compared for long term runoff simulation in the south eastern part of Iran. These models have been utilized to simulate5-month runoff in the wet period of December-April. In IHACRES application, first the rainfall is predicted using climatic signals and then transformed to runoff. For this purpose, the daily precipitation is downscaled by two models of SDSM (Statistical Downscaling Model) and LARS-WG (Long Ashton Research Station-Weather Generator). The best results of these models are selected as IHACRES model input for simulating of runoff. In application of the ANN model, effective large scale signals of SLP(Sea Level Pressure), SST(Sea Surface Temperature), DSLP and runoff are considered as model inputs for the study region. The performances of the considered models in real time planning of water resources is evaluated by comparing simulated runoff with observed data and through SWSI(Surface Water Scarcity Index) drought index calculation. According to the results, the IHACRES model outperformed ANN in simulating runoff in the study area, and its results are more likely to be comparable with the observed values and therefore, could be employed with more certainty. Downscaling, Long term runoff, Simulation, ANN, Large scale climate signals, IHACRES 328 336 http://ijce.iust.ac.ir/browse.php?a_code=A-10-435-1&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/182011/02/142012/01/232011/10/92011/10/302010/09/202010/03/17 1388/12/26 2015/10/252015/10/252015/10/252015/10/252015/10/252015/10/252012/01/102015/10/252015/10/252015/10/25 1394/8/3 M. Karamouz Director, Environmental Engineering and Science Programs Polytechnic Institute of NYU, Brooklyn, NY, Professor, School of Civil Engineering, University of Tehran, Tehran, Iran karamouz@ut.ac.ir 0031947532846009802 0031947532846009802 Yes M. Fallahi M.Sc. School of Civil Engineering., Amirkabir University of Tech.,Tehran, Iran mahdis@aut.ac.ir 0031947532846009803 0031947532846009803 No S. Nazif Assistant Professor, School of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran snazif@ut.ac.ir 0031947532846009804 0031947532846009804 No M. Rahimi Farahani M.Sc. School. of Civil Eng., Amirkabir Univ. of Tech., Tehran, Iran rahimi@aut.ac.ir 0031947532846009805 0031947532846009805 No

en The objective of this work is to perform a direct numerical simulation of turbulent channel flow where all essential scales of motion are resolved due to variable time-stepping algorithm in various time advancement method and different discritized form of convection term. A pseudo spectral method (Fourier series in stream-wise and span-wise directions and Chebychev polynomial expansion in normal direction) is employed for the spatial derivatives. The time advancement is carried out by different semiimplicit and splitting schemes. Also Alternating and Linearized forms are added to four commonly used forms of the convective term, referred to as divergence, Convection, skew-symmetric, and rotational. Spectral method based on the primitive variable formulation is used in Cartesian coordinates with two periodic and one non-periodic boundary condition in three dimensional directions ;Omega=[0,4;pi]×[-1,1]×[0,2;pi]. The friction Reynolds number for channel flow is set to be Re;tau=175 and the computational grids of 128×65×128 are used in the x, y and z directions, respectively. The comparison is made between turbulent quantities such as the turbulent statistics, wall shear velocity, standard deviation of u and total normalized energy of instantaneous velocities in different time-discretization methods and different forms of nonlinear term. The present results show that third-order timediscretizations forward Euler for explicit terms and backward Euler for implicit terms can minimize the computational cost of integration by maximizing the time step, while keeping the CFL number near a threshold in time-discretization schemes. Also, the de-aliased results of turbulence statistics do indicate that different expressions of nonlinear terms have minor discrepancy in pseudo spectral method. The results show that the most desirable approach is a combination of variable time stepping third order backward difference algorithm and rotational form, which provides reduced cost and further accuracy improvements. Channel flow, Pseudo spectral method, DNS, Time-discretization schemes, Nonlinear term forms 337 344 http://ijce.iust.ac.ir/browse.php?a_code=A-10-765-1&slc_lang=en&sid=1 2011/06/132010/09/52009/11/72009/10/182011/02/142012/01/232011/10/92011/10/302010/09/202010/03/172011/05/31 1390/3/10 2015/10/252015/10/252015/10/252015/10/252015/10/252015/10/252012/01/102015/10/252015/10/252015/10/252015/10/25 1394/8/3 M. R. Kavianpour Associate Professor, Dept. of Civil Engineering Khaje Nasir Toosi University of Technolog kavianpour@kntu.ac.ir 0031947532846009806 0031947532846009806 Yes E. Rajabi PhD candidate, Dept. of Civil Engineering Khaje Nasir Toosi University of Technology, Tehran, Iran rajabi@dena.kntu.ac.ir 0031947532846009807 0031947532846009807 No