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    Study the effect of architectural modification on fracture behavior of Al-DRA composite

    , Article Mechanics of Advanced Materials and Structures ; Vol. 21, issue. 8 , 2014 , Pages 662-668 ; ISSN: 15376494 Jamali, M ; Khalili, S ; Bagheri, R ; Simchi, A ; Sharif University of Technology
    An architectural modification method was utilized to improve fracture toughness of discontinuously reinforced aluminum (DRA) composites. Al-DRA composites having a structure similar to that of reinforced concrete were fabricated. The number of reinforcing DRA rods within Al matrix and volume fraction of SiC particles in DRA were altered to evaluate their effect on fracture behavior of these materials. It was found that architectural modification does not have any destructive influence on elastic modulus and yield strength of the composite. Moreover, the success of this method on toughness improvement strongly depends on the occurrence of debonding between Al and DRA regions upon loading  

    The seismic performance of new detailing for RCS connections

    , Article Journal of Constructional Steel Research ; Volume 91 , 2013 , Pages 76-88 ; 0143974X (ISSN) Alizadeh, S ; Attari, N. K. A ; Kazemi, M. T ; Sharif University of Technology
    Over the past few decades considerable experimental and numerical studies have been conducted on the Reinforced Concrete columns to Steel beams (RCS) connections. Most of those researches have focused on studying the joint failure modes and ultimate joint strength of specimens utilizing strong beams and columns with weak joints. In this paper, two interior RCS connections were designed based on the Strong Column-Weak Beam (SCWB) criterion. Both specimens were tested under quasi-static reversed cyclic loading. The tested specimens were modeled by a finite element method, which verified with experimental results. Several models with different joint details were investigated using the verified... 

    Comparison of nonlinear behavior of steel moment frames accompanied with RC shear walls or steel bracings

    , Article Structural Design of Tall and Special Buildings ; Volume 22, Issue 14 , 2013 , Pages 1062-1074 ; 15417794 (ISSN) Esmaeili, H ; Kheyroddin, A ; Kafi, M. A ; Nikbakht, H ; Sharif University of Technology
    In this paper, the seismic behavior of dual structural systems in forms of steel moment-resisting frames accompanied with reinforced concrete shear walls and steel moment-resisting frames accompanied with concentrically braced frames, have been studied. The nonlinear behavior of the mentioned structural systems has been evaluated as, in earthquakes, structures usually enter into an inelastic behavior stage and, hence, the applied energy to the structures will be dissipated. As a result, some parameters such as ductility factor of structure (μ), over-strength factor (Rs) and response modification factor (R) for the mentioned structures have been under assessment. To achieve these objectives,... 

    Studying higher mode effects on the performance of nonlinear static analysis methods considering near-fault effects

    , Article KSCE Journal of Civil Engineering ; Volume 17, Issue 2 , March , 2013 , Pages 426-437 ; 12267988 (ISSN) Ghahari, S. F ; Moradnejad, H. R ; Rouhanimanesh, M. S ; Sarvghad Moghadam, A ; Sharif University of Technology
    Daily development in civil engineering arena and the importance of economical aspects in the design of structures have motivated the engineers to shift their approaches from designing upon strength to designing upon performance. This is of more importance regarding the forces induced by earthquakes which have unpredicted and random nature. However, it is not possible to design or assess exactly the structural performance against strong ground motion using analytical methods which are applied for static loads and therefore precise dynamic analysis methods are needed. Despite significant progress in the analytical methods and engineering software, using nonlinear time history analysis is very... 

    FE analysis of RC structures using DSC model with yield surfaces for tension and compression

    , Article Computers and Concrete ; Volume 11, Issue 2 , 2013 , Pages 123-148 ; 15988198 (ISSN) Akhaveissy, A. H ; Desai, C. S ; Mostofinejad, D ; Vafai, A ; Sharif University of Technology
    The nonlinear finite element method with eight noded isoparametric quadrilateral element for concrete and two noded element for reinforcement is used for the prediction of the behavior of reinforcement concrete structures. The disturbed state concept (DSC) including the hierarchical single surface (HISS) plasticity model with associated flow rule with modifications is used to characterize the constitutive behavior of concrete both in compression and in tension which is named DSC/HISS-CT. The HISS model is applied to shows the plastic behavior of concrete, and DSC for microcracking, fracture and softening simulations of concrete. It should be noted that the DSC expresses the behavior of a... 

    An investigation on the effect of cement and silica fume on properties of self-compacting concrete

    , Article Proceedings of the 13th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2013 ; September , 2013 Moshiri, F ; Atashnama, A ; Panahi, M ; Gharebaghi, R ; Mahlouji, J ; Sharif University of Technology
    Hokkaido University collection of Scholarly Academic Papers, HUSCAP  2013
    Self-Compacting concrete (SCC) is identified as a high performance concrete with the ability of self compaction, using its own weight without any external vibration. SCC is able to fill congested area and voids, even in highly reinforced concrete members whilst it flows without segregation. The fresh properties of SCC such as workability can be determined using different tests including slump-flow, J ring, V-funnel, U box, L box, GTM and column technique. In this paper the effect of different amount of cementitious material, silica fume and W/C ratios on workability and compressive strength of SCC are investigated. The results indicate that the workability of mixtures is reduced by... 

    Flexural behavior of concrete beams reinforced with high volume steel fibers

    , Article ISEC 2013 - 7th International Structural Engineering and Construction Conference: New Developments in Structural Engineering and Construction ; 2013 , Pages 1031-1036 ; 9810753551 (ISBN) ; 9789810753559 (ISBN) Khaloo, A ; Jahromi, H. S ; Mohammadian, A ; Yazdani S ; Singh A ; Sharif University of Technology
    This paper presents the results of an experimental study on the flexural behavior of ten 10 × 15 × 120 (cm) steel reinforced high strength concrete beams under deflection control loading conditions. Test variable includes volumetric percentage of steel fibers (0%, 1.5%, 3%, 4%, 5%). The plain concrete strength was 30MPa. The monotonic concentrated load was applied at the center of the beam, the relative deflection was measured, and demec points were used to determine curvature of the beam. Load-deflection and moment-curvature diagrams have been obtained and plotted for each beam individually. Test results indicate that higher fiber content considerably improves flexural behavior and provides... 

    Mechanical properties of steel fiber-reinforced concrete slab tracks on non-ballasted foundations

    , Article Scientia Iranica ; Volume 20, Issue 6 , 2013 , Pages 1626-1636 ; 10263098 (ISSN) Madhkhan, M ; Entezam, A ; Torki, M. E ; Sharif University of Technology
    Sharif University of Technology  2013
    Mechanical properties of slab tracks on a foundation with nonlinear stiffness are accounted for. At first, the cracking stages were inspected in FEM models, and it was learned that slab tracks have one-way exural behavior. Secondly, experimental full-scale models were made, and the accuracy of analyses was verified by comparing the FEM loadde ection curves with those of previous studies and validating the cracking and ultimate loads with those obtained from experiments. Finally, the effects of several parameters on the cracking and ultimate loads and the energy absorption of steel fiber-reinforced slab tracks were investigated by examining the real behavior of slab tracks on elastic... 

    Experimental investigation of square RC column strengthened with near surface mounted GFRP bars subjected to axial and cyclic lateral loads

    , Article Scientia Iranica ; Volume 20, Issue 5 , 2013 , Pages 1361-1371 ; 10263098 (ISSN) Dayhim, N ; Nicknam, A ; Barkhordari, M. A ; Hosseini, A ; Mehdizad, S ; Sharif University of Technology
    Sharif University of Technology  2013
    This article is intended to highlight the effectiveness of longitudinal Glass Fiber Reinforced Polymer (GFRP) bars in combination with GFRP sheets on the flexural capacity of Reinforced Concrete (RC) columns. Seven half-scale RC columns including five strengthened and two control unstrengthened specimens were experimentally tested under axial and cyclic lateral loads. The strengthened columns with two different longitudinal GFRP bar ratios were tested under three different axial load levels. The flexural strength and ductility parameters of the specimens were calculated by obtaining their deformations and measuring the loads from load cells. The experimental results indicate significant... 

    The corrosion investigation of rebar embedded in the fibers reinforced concrete

    , Article Construction and Building Materials ; Volume 35 , October , 2012 , Pages 564-570 ; 09500618 (ISSN) Kakooei, S ; Akil, H. M ; Dolati, A ; Rouhi, J ; Sharif University of Technology
    Elsevier  2012
    One effective method for preventing corrosion of steel reinforcement and improving the mechanical properties of concrete is changing the physical nature of concrete by adding different materials. In this study, we have used polypropylene fibers as an additional material. We have compared the corrosion rate of rebar using different volume ratios and sizes of polypropylene fibers. Reinforcement potential increased as the amount of fibers increased from 0 to 2 kg m -3. The polypropylene fibers delay the initial corrosion process by preventing cracking, thereby decreasing permeability of the concrete. In addition, the corrosion rate of concrete samples made with Kish Island coral aggregate was... 

    An efficient performance-based seismic design method for reinforced concrete frames

    , Article Earthquake Engineering and Structural Dynamics ; Volume 41, Issue 4 , 2012 , Pages 663-679 ; 00988847 (ISSN) Hajirasouliha, I ; Asadi, P ; Pilakoutas, K ; Sharif University of Technology
    In this paper, a practical method is developed for performance-based design of RC structures subjected to seismic excitations. More efficient design is obtained by redistributing material from strong to weak parts of a structure until a state of uniform deformation or damage prevails. By applying the design algorithm on 5, 10 and 15-storey RC frames, the efficiency of the proposed method is initially demonstrated for specific synthetic and real seismic excitations. The results indicate that, for similar structural weight, designed structures experience up to 30% less global damage compared with code-based design frames. The method is then developed to consider multiple performance objectives... 

    Response of reinforced concrete structures to macrocell corrosion of reinforcements. Part II: After propagation of microcracks via a numerical approach

    , Article Nuclear Engineering and Design ; Volume 242 , 2012 , Pages 7-18 ; 00295493 (ISSN) Kiani, K ; Shodja, H. M ; Sharif University of Technology
    Investigation of response of reinforced concrete (RC) structures due to axisymmetric macrocell corrosion of rebars is of concern after propagation of microcracks within the concrete medium. The geometry, boundary and interfaces conditions of the present problem are identical to those stated in part I. As seen in the companion paper, the exact solution to the boundary value problem corresponding to the uncracked steel-rust-concrete composite was possible. After appearance of the microcracks the concrete behavior becomes nonlinear anisotropic with post-cracking softening, and the associated problem is analytically intractable. Therefore, it is proposed to employ a novel meshless method, namely... 

    Response of reinforced concrete structures to macrocell corrosion of reinforcements. Part I: Before propagation of microcracks via an analytical approach

    , Article Nuclear Engineering and Design ; Volume 241, Issue 12 , 2011 , Pages 4874-4892 ; 00295493 (ISSN) Kiani, K ; Shodja, H. M ; Sharif University of Technology
    Assessment of the macrocell corrosion which deteriorates reinforced concrete (RC) structures have attracted the attention of many researchers during recent years. In this type of rebar corrosion, the reduction in cross-section of the rebar is significantly accelerated due to the large ratio of the cathode's area to the anode's area. In order to examine the problem, an analytical solution is proposed for prediction of the response of the RC structure from the time of steel depassivation to the stage just prior to the onset of microcrack propagation. To this end, a circular cylindrical RC member under axisymmetric macrocell corrosion of the reinforcement is considered. Both cases of the... 

    Mixed mode fracture in reinforced concrete with low volume fraction of steel fibers

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 24, Issue 1 , February , 2011 , Pages 1-18 ; 1728-144X (ISSN) Kazemi, M. T ; Zakeri, I ; Shahvari, F. V ; Sharif University of Technology
    Materials and Energy Research Center  2011
    An investigation into the mixed mode fracture of steel fiber reinforced concrete (SFRC) beams with one percent volume fraction of steel fiber is presented. A series of notched beams with different notch depths and locations are tested under three-point bending. The test results for apparent fracture toughness, crack trajectories, and fracture energy are presented. The crack paths for SFRC and plain concrete beams are compared. The apparent fracture toughness values were more scattered for SFRC than for plain concrete. The load-deflection curves were used to obtain the fracture energy. To this end, two methods were utilized for center notched beams, and the results were comparable to each... 

    A precise solution for prediction of fiber-reinforced concrete behavior under flexure

    , Article Journal of Zhejiang University: Science A ; Volume 12, Issue 7 , 2011 , Pages 495-502 ; 1673565X (ISSN) Ahmadi, R ; Ghoddousi, P ; Sharifi, M ; Bahreh, V. M ; Sharif University of Technology
    This paper presents a precise solution to predict the behavior of steel fiber reinforced concrete (SFRC) under the four point bending test (FPBT). All the force components at the beam section (before and after cracking) are formulated by applying these assumptions: a realistic stress-strain model is used for concrete behavior in compression, a linear response is considered for the uncracked tension region in a concrete constitutive model, and an exponential relationship is proposed as a stress-crack opening in the crack region which requires two parameters. Then the moment capacity of the critical cracked section is calculated by using these forces and satisfying equilibrium law at the... 

    On the modal incremental dynamic analysis of reinforced concrete structures, using a trilinear idealization model

    , Article Engineering Structures ; Volume 33, Issue 4 , 2011 , Pages 1117-1122 ; 01410296 (ISSN) Zarfam, P ; Mofid, M ; Sharif University of Technology
    In order to estimate the seismic demands at the performance level, the inelastic behavior of concrete structures should be considered. Incremental dynamic analysis (IDA) based on a nonlinear response time history analysis (NL-RHA) is considered to be the most accurate method in seismic demand calculations. However, modal incremental dynamic analysis (MIDA), based on the equivalent single-degree-of-freedom (SDF) oscillator, is also often used in studying structural engineering performances. As the MIDA method has usually not been applied to reinforced concrete (RC) structures, in this study an attempt is made to investigate the performances of RC frames and to compare the results obtained... 

    Mechanical properties of precast reinforced concrete slab tracks on non-ballasted foundations

    , Article Scientia Iranica ; Volume 19, Issue 1 , February , 2012 , Pages 20-26 ; 10263098 (ISSN) Madhkhan, M ; Entezam, M ; Torki, M. E ; Sharif University of Technology
    This article deals with the mechanical properties of steel-reinforced concrete precast slab tracks on non-ballasted elasto-plastic foundations. To work out the spanning behavior of slab tracks, a FEM analysis was executed for discrete and continuous systems. At first, full-size slabs without foundation including solid and hollow-core specimens (with 30% weight reduction) were tested under centric static (monotonic) line loads, and loaddeflection curves were extracted. Then, FEM results for zero foundation stiffness were verified with those of experiments, which were in good agreement. Original results include the effects of several parameters on the cracking load, ultimate load, and energy... 

    The effect of transverse steel and FRP jacket confinement on mechanical properties of concrete cylinders: An experimental study

    , Article ISEC 2011 - 6th International Structural Engineering and Construction Conference: Modern Methods and Advances in Structural Engineering and Construction ; 2011 , Pages 827-832 ; 9789810879204 (ISBN) Khaloo, A. R ; Javid, Y ; Khosravi, H ; Yazdani S ; Cheung S. O ; Singh A ; Ghafoori N ; American Society of Civil Engineers (ASCE); Architectural Institute of Japan (AIJ); Chartered Institute of Building (CIOB); et al.; University of Nevada Las Vegas (UNLV), College of Engineering; Wayne State College of Engineering ; Sharif University of Technology
    This paper presents the results of an experimental study on the behavior of concrete cylinders externally wrapped with fiber-reinforced polymer (FRP) composites and internally reinforced with steel spirals. The experimental work was performed by testing 30 concrete cylinders (120 × 400mm2) subjected to pure compression to achieve the complete stress-strain curve. Test specimens were confined with various internal and external confinement ratios and different types of confining material such as steel, Carbon FRP (CFRP) and Glass FRP (GFRP). The compressive strength, corresponding strain and the complete stress-strain curve of the tested specimenswere indicated. The test results showthat the... 

    Mechanical properties of fiber-reinforced high-performance concrete incorporating pyrogenic nanosilica with different surface areas

    , Article Construction and Building Materials ; Volume 101 , December , 2015 , Pages 130-140 ; 09500618 (ISSN) Mobini, M. H ; Khaloo, A ; Hosseini, P ; Esrafili, A ; Sharif University of Technology
    Elsevier Ltd  2015
    The aim of the present study was to investigate the effect of pyrogenic nanosilica with different specific surfaces areas (200 and 380 m2/g) on mechanical properties of fiber-reinforced high-performance concrete (FRHPC) produced with two different types of fibers including steel and polypropylene fibers. Accordingly, different mechanical tests (compressive, splitting tensile and flexural strengths) as well as electrical resistivity were performed at 7, 28, and 91 curing days. In addition, the modulus of rupture and flexural toughness of FRHPC prisms were calculated based on the flexural testing results. Also, scanning electron microscopy test (SEM) was conducted to evaluate the... 

    Seismic Rehabilitation of Reinforced Concrete Structures Using Eccentric Steel Bracing

    , M.Sc. Thesis Sharif University of Technology Rajaee Mohammadiye, Kourosh (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    The seismic performance of a low-rise nonductile reinforced concrete (RC) building rehabilitated using eccentric steel bracing is investigated. At first three-story building was Modeled using sap 2000 computer program then analyzed and getting the results. The effectiveness of the eccentric steel bracing in rehabilitating the building was examined. The effect of distributing the steel bracing over the height of the RC frame on the seismic performance of the rehabilitated building was studied. The behavior of the nonductile RC frame members is represented by a beam–column element capable of modeling the strength deterioration and the effect of the axial force on the yield moment and the...