@article { author = {Bakhshi, N. and Sarrafi, A. and Ramezanian pour, A.A.}, title = {Chromate Ion Transfer Through Mortar by Accelerated Migration Method}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {3-12}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14835.5501}, abstract = {Chromium (VI) is a highly toxic heavy metal which may be present in cementitious materials (CM) within its constituting elements or external sources and could alter the structure of CM and reduce its compressive strength. Therefore penetration of chromium is an important consideration in environmental engineering concrete structures. For estimating diffusivity of chromium (chromate ion) in cementitious materials, this paper presents an accelerated migration test method for determining the non-steady-state migration coefficient following the simplified Nernst-Planck equation. Likewise, the influence of water-to-cement ratio (w/c), the applied voltage the chromium binding capacity of cement mortar specimen (CMS) and the realistic concentration profile was investigated. For calculation of migration coefficient, the color reagent diphenylamine sulfonate was identified to determine the penetration depth of chromium into the CMS visually. The concentration of chromium was estimated to be about 0.025 percent (wt of CMS) at the discolored border region, and a drop of potential about 3.4 volts was derived. The changes in the microstructure of the CMS due to chromium migration testing were studied. The migration coefficient of CMS obtained between 1.06×10-12 m2/s to 3.25×10-12 m2/s. The w/c of about 0.50 has the highest migration coefficient. The realistic chromium concentration profile in the migration test has a gradual front, and a quadratic curve obeys.}, keywords = {chromate ion,cementitious materials,migration coefficient,profile}, url = {https://ajce.aut.ac.ir/article_3126.html}, eprint = {https://ajce.aut.ac.ir/article_3126_6a00d70893897ea4262d8032a7a5ce3c.pdf} } @article { author = {Z. BEYDOKHTI, E. and Khatibi, S.H. and yousefi, Mehdi}, title = {Cyclic Behaviour of the Knee Braced System Considering the Type of Knee Joint}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {13-22}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.15016.5515}, abstract = {In recent years, the use of braced frame systems has been expanded to achieve a stiff and ductile structures in high seismic zones. Among the various types of bracing systems, the knee bracing system has been specially considered for seismic design in steel structures. In this system, the diagonal member provides the system’s stiffness, and the knee member as a fuse, provides the ductility and prevents the buckling of diagonal member; Thus, it is expected that the stiffness and ductility of the structures will be remained simultaneously. In this study, the knee braced frames modelled using finite element method under statically cyclic loading. The effect of different types of the joints between the diagonal members to the knee member on cyclic behaviour of the knee bracing system was investigated. Three fixed joints were: the diagonal connected to flange of a continuous knee member (KBF-1), the diagonal connected to the web of discontinuous knee member (KBF-2) and the diagonal connected to the web of discontinuous knee member with stiffener (KBF-3). The results showed that KBF-3 model had better performance in terms of ductility, energy absorption and ultimate capacity. Besides, the elastic stiffness of KBF-2 and KBF-3 joints were approximately the same.}, keywords = {Knee bracing system,fixed joint,cyclic behavior,steel structure,Ductility}, url = {https://ajce.aut.ac.ir/article_3123.html}, eprint = {https://ajce.aut.ac.ir/article_3123_698883362b0a3aa94f99a3a6eafe0d97.pdf} } @article { author = {Shahraki, M. and sohrabi, M.R. and Azizian, Gh. and Narmashiri, K.}, title = {Reliability Assessment of CFRP-Strengthened Deficient Steel SHS Columns}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {23-36}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14939.5506}, abstract = {Civil engineers have always been vexed by such numerous problems such as buckling, corrosion, bending, and over-loading in damaged steel structures. The present study is aimed to evaluate the effects of the axial loading, axial displacement, stiffness and deficiency location on the length of the deficient steel SHS columns have been evaluated based on a detailed parametric study. Three specimens were tested to failure under axial compression in the lab and simulated using the Finite Element (FE) numerical approach and a total of 100 samples were analyzed by ABAQUS using the MATLAB software to predict the suitable limit state functions and determine the best R2 value through such soft computing techniques as the Artificial Neural Networks, Adaptive Neuro-Fuzzy Inference System, Response Surface Method, and Gene Expression Programming. Finally, the failure probability and reliability index were obtained by the FORM and Monte Carlo methods on the suggested limit state functions. Results indicated that using CFRP sheets reduced the stress in the damaged location and appropriately prevented or delayed local deformations around the deficient location. So, strengthening steel columns with CFRP can play a significant role in enhancing the rate of the critical load and β, and reducing (Pf ), in deficient columns.}, keywords = {Square Hollow Section (SHS) Steel Column,Deficient,CFRP,reliability assessment,Probability failure}, url = {https://ajce.aut.ac.ir/article_3122.html}, eprint = {https://ajce.aut.ac.ir/article_3122_ca01d3e0ad806224c72b111967e681a0.pdf} } @article { author = {Abhari, S. and Barghian, M.}, title = {Theoretical Assessment of the Behavior of a Cable Bracing System with a Central Steel Plate}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {37-48}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.15249.5527}, abstract = {The large displacements and lack of sufficient lateral stiffness are the main problems of moment resisting frames (MRFs). In this research a system of four cable bracings connected to a square steel plate located in the center of them has been studied to solve MRF’s mentioned problems. The theoretical behavior of the system was derived under a lateral static load. The purpose of this study is to demonstrate the efficiency of the system, in which all cables have tensile forces under the lateral load and cables are not slackened. The cables diameter and plate dimensions were investigated. It was observed that the variation of cable diameter had a significant effect on the frame lateral displacement; while the variation of dimensions of the plate did not have much effect on the obtained values. The results showed that the proposed system had the same characteristics of the MRF for its appropriate ductility, at the same time it had its high stiffness. Adding a steel plate in the center of bracings causes all cables to involve against the lateral load and all cables remain in tension. Therefore, using the central steel plate improves the performance of the structure against the applied lateral load.}, keywords = {Cable,plate,Bracing,Retrofit,Assessment}, url = {https://ajce.aut.ac.ir/article_3120.html}, eprint = {https://ajce.aut.ac.ir/article_3120_3af7d7d53fdd696228fc000dbb72a463.pdf} } @article { author = {Morshed, R. and Shayegh, H.R. and Mirjalili, M.R.}, title = {Experimental and Analytical Study of new Proposed Semi-rigid Concrete Bam-toColumn Connection}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {49-60}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14987.5511}, abstract = {A new semi-rigid concrete beam-column connection is proposed and its performance is investigated through experimental and analytical studies. In this connection, the beam dose not directly connect to column but it is connected with torsional link member. This scissor mechanism allows the beam to make rotation with respect to column. Moreover, the strengthened connections are also suggested to support higher levels of lateral deformations for structures located in high risk seismic areas. The connections behavior under cyclic loads has been studied experimentally using three types of specimens; i) basic specimen, ii) strengthened specimen with Carbon Fiber Reinforced Polymer (CFRP) wrapping, iii) strengthened specimen with steel core reinforcing. The results showed that for low levels of deformations, the basic connection exhibited acceptable performance but for higher levels of rotation, the strengthened specimens had significant merits in ductility and nonlinear characteristics. Beside the experimental tests, the numerical model of connection was constructed using ABAQUS program. The accuracy of modeling was verified through experimental results. To investigate the effect of using proposed semi-rigid connection in seismic demands of concrete structures, two rigid and semi-rigid three-story frames were modeled in OpenSees. Several nonlinear dynamic analyses were carried on models and the different global and local demands were compared. The results showed that in low-rise or non-sway buildings in which the lateral displacements are not very considerable, semi-rigid connections can lead to smaller seismic loads and consequently the economical and optimal design.}, keywords = {Concrete semi-rigid connection,Beam-to-column Connection,Torsion in Concrete Beams,torsional behavior,torsional connection}, url = {https://ajce.aut.ac.ir/article_3118.html}, eprint = {https://ajce.aut.ac.ir/article_3118_c5111d9b54bc63a09075edcad106d25a.pdf} } @article { author = {Jafari, M.A. and Zekavati, A.A.}, title = {Calibration of Safety Factor for Micropile in Transmission Tower Foundations Based on Relative Reliability Approach}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {61-74}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.15057.5519}, abstract = {This paper determines the design safety factor of micropiles utilized in the foundation of electric power transmission towers against the geotechnical failure due to the compressive force (failure of micropile-soil cohesion) by using the relative reliability approach. On the basis of this approach, the design processes are conducted in a way so that the reliability of foundation would be greater than that of tower. In other words, the failure of tower structure should occur prior to that of foundation. In order to calculate the safety factors in terms of specific reliability level of foundation with respect to tower, reliability analyses were adopted using “Monte Carlo Sampling” method. Furthermore, the strength statistical characteristics of transmission towers and micropiles have been extracted based on the reports of previous tests. The results of which revealed that, considering the target value of Relative Reliability Factor (RRF)- the ratio between failure probabilities of tower to foundation- as 12, the values of safety factors attained in the current research are equal to 2.0 and 2.20 respectively for lattice and pole transmission towers. It should be remarked that these safety factors are only valid in cases of micropile design in dense sandy (SP-SM, SP&GW-GM) and clay-silt (SC, SM&SC-SM) soils.}, keywords = {Safety factor,relative reliability,transmission line,micropile,geotechnical design}, url = {https://ajce.aut.ac.ir/article_3117.html}, eprint = {https://ajce.aut.ac.ir/article_3117_1c1a59f7e35410d75b8e34293238fc4c.pdf} } @article { author = {Soleimanian, M. and Kilanehei, F. and Memarpour, M. M.}, title = {Comparison of Wind Speed-Up over Escarpments Derived from Numerical Modeling and Wind-Loading Codes}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {75-84}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14996.5513}, abstract = {The most common lateral load is a wind load. The wind speed profile considers as an effective parameter to find the wind load. Topographic features such as escarpments and hills in flat area can significantly amplify wind speeds near the ground. The main aim of this study is to investigate the effects of the escarpment characteristics on the velocity profile and speed-up using the numerical model. At the first, the numerical model validated with the experimental results obtained through the wind tunnel of Texas University. Then, three kinds of escarpments with different slopes simulated and speed-ups obtained from the numerical model, wind tunnel, ASCE and Iran codes compared. The results of numerical model at the smaller slope showed better accordance with wind tunnel results. The effect of inlet velocity profile on the speed-up was numerically studied. Comparison of the results showed that the maximum speed-up using the velocity profile of Iran code is greater than using ASCE code. Finally, the effect of the escarpment height and width with the same slope on speed-up was investigated. The results showed that speed-up grows as the width and height increase; however, the effect of increasing the height is less.}, keywords = {Wind velocity profile,Speed-up,Escarpment,Numerical modeling,Design code}, url = {https://ajce.aut.ac.ir/article_3114.html}, eprint = {https://ajce.aut.ac.ir/article_3114_84328100db20567decd6a34c539be796.pdf} } @article { author = {Saeidipour, M. and Radmanesh, F. and Eslamian, S.}, title = {Meteorological Drought Monitoring Using the Multivariate Index of SPEI (Case Study: Karun Basin)}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {85-92}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14740.5494}, abstract = {Considering the importance of drought in water resources management, the present study was conducted with the aim of drought monitoring using drought index SPEI due to its multi-scale nature and the ability to analyze at different time scales in selected meteorological stations in the Karun drainage basin. Another purpose of this research is to regionalize the SPEI index using cluster analysis method in order to homogenize the hydrologic basin. In this regard, 18 stations were selected based on the data homogeneity test and the determination of the length of the common statistical period. The SPEI drought index values were plotted in the form of sequencing graphs and their relationship with the correlation analysis was tested. The results showed that there is a positive and significant correlation of this index for all stations (0.5 to 0.95). Also, the frequency of dry and wet periods decreases by increasing the time scale, but their continuity increases. With the regionalization of the basin stations by cluster analysis, the stations were classified into 7 classes. The results of regionalization of the SPEI index also showed that the frequency percentage of the normal class is higher than the wet and dry classes.}, keywords = {Evapotranspiration,Dry and wet periods,SPEI index,Basin regionalization,Cluster Analysis}, url = {https://ajce.aut.ac.ir/article_3094.html}, eprint = {https://ajce.aut.ac.ir/article_3094_753464d0d8514ed6b5dd61e2afc9426b.pdf} } @article { author = {Golmohammadi, M. and ghalehnovi, M. and yousefi, M.}, title = {Experimental Investigation of Steel-concrete-steel Slabs with Stud Bolt Connectors Subjected to Punching Loading}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {93-106}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14763.5496}, abstract = {Steel-Concrete-Steel (SCS) sandwich structures are composed of two steel face plates and one concrete core. SCS as slab has more advantages than reinforced concrete (RC) slab that their most important are impermeability and higher resistance against impact loads. SCS sandwich slabs are widely employed in civil engineering and onshore and offshore structures due to their better performance and advantages. Mechanical connectors are used for better performance of the slabs. In the present research, stud bolt connectors are used together with nuts. The core is composed of ordinary concrete. Nine test samples of SCS slabs are made with stud bolt connectors and are put under concentrated load at the center of the slab. The observed failure modes included concrete core crack, lower plate slip and upper plate buckling, and stud bolt separation. To study load vs. displacement at the center and load vs. interlayer slip behavior, stud bolts diameter and concrete thickness were varied. The results of the tests were compared with the results of sandwich slabs with J-hook connectors and a better behavior was observed. One theoretical model was used to predict the bending strength of the slabs. The results of the theoretical model were consistent with test results.}, keywords = {Bending strength,double-sided cutting,failure modes,SCS sandwich slab,stud bolt connector}, url = {https://ajce.aut.ac.ir/article_3093.html}, eprint = {https://ajce.aut.ac.ir/article_3093_788ea8ce73ad5511333dd6005757c18b.pdf} } @article { author = {Hamedi, Gh.H. and Esmaeili, N.}, title = {Investigating of the Effects of Nano-materials on the Moisture Susceptibility of Asphalt Mixtures Containing Glass Cullets}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {107-118}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14665.5492}, abstract = {The pavement industry is one of the industries that has considered using waste to partially replace the aggregates in asphalt mixtures. Despite its many environmental and technical benefits, the use of crushed glass increases the moisture damage potential of asphalt mixtures. Therefore, in the present study, the aim was to investigate the effects of two nano anti-stripping additives called nano iron oxide (Fe2O3) and nano aluminum oxide (Al2O3) on the moisture susceptibility of hot mix asphalt (HMA) mixtures containing crushed glass. The glass asphalt mixtures were made by replacing 0, 5, 10, 15, and 20% of the fine aggregates with glass cullets. In order to investigate the effects of nano-materials on the moisture susceptibility of glass asphalt mixtures, the modified Lottman test (AASHTO T283) and the surface free energy (SFE) method were used. The results showed that the addition of nano-materials improved the adhesive force between asphalt binders and aggregates (crushed glass and aggregates with acidic properties) by reducing the acidic and increasing the basic properties of the modified asphalt binder. Moreover, asphalt modification with nano-materials increased the initial energy required to separate asphalt binder from the aggregate surface and reduced the risk of moisture damage by increasing the total SFE of asphalt binder.}, keywords = {Glass asphalt mixture,moisture damage,nano-additives,modified Lottman,surface free energy}, url = {https://ajce.aut.ac.ir/article_3081.html}, eprint = {https://ajce.aut.ac.ir/article_3081_32deb4c84ee322739af2634bcc0dd1bf.pdf} } @article { author = {Behnamfar, F. and Naseri-Dehkordi, A.}, title = {Modal Non-linear Static Analysis of Structures Based on Story Shears}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {119-128}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14614.5488}, abstract = {In this paper a modal pushover procedure is presented in which distribution of lateral forces is calculated using the story shears. The shear force of each story is determined using its relative interstory displacement and stiffness in each mode of vibration utilizing spectral analysis relations. To retain simplicity of the procedure, like the common pushover procedures, the initial elastic dynamic characteristics of buildings are used for spectral analysis throughout. A combination rule for modal story shears is proposed that keeps the signs of responses. Therefore, the computed lateral loads contain effects of the desired number of modes and the nonlinear static analysis is performed in a single stage accounting for effects of higher modes. The lateral displacements, story shears and cumulative plastic hinge rotations are compared with the results of the conventional and modal pushover analysis and with the result of the exact nonlinear dynamic analysis. The comparative study establishes good accuracy of the proposed method as an alternative modal pushover procedure.}, keywords = {Pushover,shear based,modal,conventional,time history,nonlinear}, url = {https://ajce.aut.ac.ir/article_2974.html}, eprint = {https://ajce.aut.ac.ir/article_2974_8668e3f9541e3626424389a6159457e6.pdf} } @article { author = {Akbarimehr, D. and Aflaki, E.}, title = {Using Empirical Correlations to Evaluate the Compression Index of Tehran Clay}, journal = {AUT Journal of Civil Engineering}, volume = {3}, number = {1}, pages = {129-136}, year = {2019}, publisher = {Amirkabir University of Technology}, issn = {2588-2899}, eissn = {2588-2902}, doi = {10.22060/ajce.2018.14522.5482}, abstract = {Correlations between different parameters are used extensively in geotechnical engineering. Using correlations reduces the costs of testing and more speeds in determining the geotechnical properties of soils. Various relations have been proposed to evaluate geotechnical properties in different regions across the globe. Correlations facilitate the evaluation of geotechnical properties. The correlation between different parameters depends on the type of the soil and the experimental method. Considering the fact that these relations depend on local soil properties, using these relations for other regions is contingent upon a careful evaluation. This study evaluates the feasibility of using correlations presented by researchers in different years for Tehran clay. The evaluation uses different statistical criteria. The study shows the Bowles (1979) relation, correlating the soil compression index and the initial void ratio, is the best fit for Tehran clay among the studied correlations. In addition, the quality of the correlations can be evaluated for Tehran clay. Correlations between the soil compression index and initial void ratio often estimate the compression index with acceptable accuracy while correlations between the compression index and other geotechnical properties, such as the initial water content, plasticity index, shrinkage index, the liquid limit, and the soil density, are less accurate.}, keywords = {Compression Index,Physical Properties,Correlation,Tehran Clay,Consolidation Test}, url = {https://ajce.aut.ac.ir/article_2928.html}, eprint = {https://ajce.aut.ac.ir/article_2928_34f4487ba23c57ce2d53d01048f80cce.pdf} }