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    Experimental study of RC jacketed and CFRP strengthened RC beams

    , Article Construction and Building Materials ; Volume 95 , October , 2015 , Pages 476-485 ; 09500618 (ISSN) Tahsiri, H ; Sedehi, O ; Khaloo, A ; Raisi, E. M ; Sharif University of Technology
    Elsevier Ltd  2015
    This paper presents the results of an experimental study on retrofitting RC beams using FRP strengthening and RC jacketing. Three-point loadings are applied to twelve strengthened beams and three reference specimens to put the two techniques into perspective. Formation of first cracks, FRP debonding, and onset of concrete crushing are compared and discussed. Load-deflection behavior, failure modes, and crack propagation patterns are studied extensively. The experiments demonstrate that the RC jacketed beams exhibit a flexural failure identical to the reference beams. However, the FRP strengthened beams fail in a relatively small deflection due to the premature FRP debonding. Furthermore, the... 

    Seismic rehabilitation of exterior RC beam-column joints using steel plates, angles, and posttensioning rods

    , Article Journal of Performance of Constructed Facilities ; Volume 30, Issue 1 , 2016 ; 08873828 (ISSN) Arzeytoon, A ; Hosseini, A ; Goudarzi, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    The presented studies have been conducted on the scope and magnitude of damages inflicted by earthquakes over the years. Many RC buildings, designed and constructed in the 1960s and 1970s, have serious structural deficiencies, especially in their beam-column joints. Such deficiencies result from inadequate joint shear strength or confinement of column reinforcement. The joints require elaborate retrofit measures to ensure the performances comparable to those of new designed structures. In this research, a new seismic retrofitting method is presented for beam-column joints based on the two-dimensional enlargement of the joint by using steel plate, angles, and posttensioning rods. The seismic... 

    Behavior of reinforced concrete beams post-tensioned in the critical shear region

    , Article Engineering Structures ; Volume 29, Issue 7 , 2007 , Pages 1465-1474 ; 01410296 (ISSN) Shamsai, M ; Sezen, H ; Khaloo, A. R ; Sharif University of Technology
    A new shear strengthening method involving post-tensioning of the critical shear region of reinforced concrete beams is investigated. Thirty-one experiments were carried out using 24 specimens. Theoretical load-deflection relations are obtained from moment-curvature analysis using fiber cross sections and taking into consideration the effects of different concrete confinements along the beam length. A theoretical shear strength model that includes three shear resisting components in the critical shear region of the strengthened beams is provided. Experimental results from beams with and without shear strengthening are compared with calculated load-deflection relations and predicted shear... 

    Nonlinear seismic assessment of steel moment frames under bidirectional loading via endurance time method

    , Article Structural Design of Tall and Special Buildings ; Vol. 23, issue. 6 , April , 2014 , p. 442-462 ; ISSN: 15417794 Valamanesh, V ; Estekanchi, H. E ; Sharif University of Technology
    In this paper, considering horizontal components of seismic excitation, an algorithm for the nonlinear multi-component analysis of building structures by the Endurance Time (ET) method is proposed, and results of the ET method for various steel moment frames with one to seven stories are verified by comparing with the results from Nonlinear Time History Analysis with use of two different sets of ground motions. In addition, several parameters such as eccentricities and irregularities in structure, rotational and lateral stiffness, effect of hysteresis type and ductility have been considered for sensitivity analysis on results, obtained by ET method. Results show that on the basis of... 

    Response modification factors of steel moment frames equipped with completely closed ribbed bracing system (CC-RBS)

    , Article Advances in Structural Engineering ; Volume 15, Issue 7 , 2012 , Pages 1083-1097 ; 13694332 (ISSN) Tabeshpour, M ; Golafshani, A ; Shalmani, A ; Sharif University of Technology
    In this paper completely closed RBS (CC-RBS) is proposed as a function of a new ribbed bracing system (RBS). RBS is an innovative system which has capacity of performing variable stiffness that can be used for controlling structural deformations and frequency shifting to compensate seismic energy. The overstrength, ductility, and response modification factors of steel moment frames equipped with CC-RBS was evaluated by performing pushover analysis of model structures with various stories and compared with those which Iranian seismic code of practice, Standard No. 2800 is supposed for steel moment frame equipped with ordinary brace.The results were compared with those from nonlinear... 

    Collapse assessment of steel moment frames using endurance time method

    , Article Earthquake Engineering and Engineering Vibration ; Volume 14, Issue 2 , 2015 , Pages 347-360 ; 16713664 (ISSN) Rahimi, E ; Estekanchi, H. E ; Sharif University of Technology
    Institute of Engineering Mechanics (IEM)  2015
    In endurance time (ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specified spectrum, intensifies with time so they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this paper applicability of the ET method for evaluating collapse potential of buildings is investigated. A set of four steel moment frames is used for collapse assessment. The process of using ET method in collapse evaluation is explained and the results are compared with incremental dynamic analysis (IDA) results. It is shown... 

    Nonlinear interstory drift contours for idealized forward directivity pulses using "modified fish-bone" models

    , Article Advances in Structural Engineering ; Volume 18, Issue 5 , May , 2015 , Pages 603-627 ; 13694332 (ISSN) Khalo, A. R ; Khosravi, H ; Jamnani, H. H ; Sharif University of Technology
    Multi-Science Publishing Co. Ltd  2015
    Four 5-, 10-, 20- and 30-story moment frames, representing low-, mid-, and two high-rise structures, were subjected to a great number of idealized directivity pulses. The amplitudes and periods of pulses vary from 0.02 g to 1.0 g and 0.5 to 12 sec, respectively. Over 1400 nonlinear dynamic analyses of low- to high-rise moment frames were performed which were feasible through using modified fish-bone model. The distribution of interstory drift along the height was studied and two applied contours were proposed: (i) the maximum interstory drift contour, and (ii) the critical story contour. These contours were demonstrated versus the ratio of natural period of the structure to the pulse period... 

    A model for the evolution of concrete deterioration due to reinforcement corrosion

    , Article Mathematical and Computer Modelling ; Volume 52, Issue 9-10 , November , 2010 , Pages 1403-1422 ; 08957177 (ISSN) Shodja, H. M ; Kiani, K ; Hashemian, A ; Sharif University of Technology
    One of the most crucial factors affecting the service life of reinforced concrete (RC) structures attacked by aggressive ions is reinforcement corrosion. As the steel corrosion progresses, crack propagation in concrete medium endangers the serviceability and the strength of RC structural members. In this study, a nonlinear mathematical model for determining the displacement and stress fields in RC structures subjected to reinforcement corrosion is introduced. For corrosion products, a nonlinear stress-strain relation which has been previously confirmed by experimental data is incorporated in the present analysis. In formulation of the governing equations for steel-rust-concrete composite,... 

    Cyclic behaviour of interior reinforced concrete beam-column connection with self-consolidating concrete

    , Article Structural Concrete ; Volume 17, Issue 4 , 2016 , Pages 618-629 ; 14644177 (ISSN) Salehi Mobin, J ; Kazemi, M. T ; Attari, N. K. A ; Sharif University of Technology
    A significant amount of research on self-consolidating concrete (SCC) technology has been devoted to evaluating the suitability of the material for its use in structural applications. However, more research is required to confirm the adequacy of SCC structural members for resisting gravity and seismic loads. This study focuses on the experimental investigation of the seismic performance of interior reinforced concrete beam-column connections with SCC. Four beam-column connection specimens, three with SCC and one with normally vibrated concrete (NC), were designed for this experimental study. Factors such as concrete type (SCC or NC) and axial load ratio (0, 7.5 and 15 % of column section... 

    Coupling microplane-based damage and continuum plasticity models for analysis of damage-induced anisotropy in plain concrete

    , Article International Journal of Plasticity ; Volume 95 , 2017 , Pages 216-250 ; 07496419 (ISSN) Daneshyar, A ; Ghaemian, M ; Sharif University of Technology
    Elsevier Ltd  2017
    A novel plastic-damage constitutive model for plain concrete is developed in this paper. For this purpose, the microplane theory is proposed for overcoming the deficiency of available anisotropic continuum plastic-damage models in reproducing the true anisotropic nature of damage in multidimensional loadings. Based on the microplane theory, the degeneration process in concrete is considered along with plastic deformations. Using the principle of strain energy equivalence, a transformation between the nominal and effective states of material is achieved, that results in a decoupled formulation for damage and plasticity. A yield function with multiple internal variables and a non-associative... 

    Seismic performance of reduced web section moment connections

    , Article International Journal of Steel Structures ; Volume 17, Issue 2 , 2017 , Pages 413-425 ; 15982351 (ISSN) Momenzadeh, S ; Kazemi, M. T ; Hoseinzade Asl, M ; Sharif University of Technology
    Korean Society of Steel Construction  2017
    Seismic behavior of beam-to-column connections can be improved by shifting the location of inelasticity away from the column’s face. Such connections can be achieved by reducing the flange area at a specific distance from the beam-column connection, called reduced beam section (RBS), or by reducing web area by introducing a perforation into the web, called reduced web section (RWS). This paper presents a parametric study that is carried out on the effect of the perforation size, perforation location, and the beam span length in the RWS connections, using finite element modeling. Next, an interaction formula is derived for design purposes, and a step by step design method is developed.... 

    Monotonic behavior of C and L shaped angle shear connectors within steel-concrete composite beams: An experimental investigation

    , Article Steel and Composite Structures ; Volume 35, Issue 2 , 2020 , Pages 237-247 Shariati, M ; Tahmasbi, F ; Mehrabi, P ; Bahadori, A ; Toghroli, A ; Sharif University of Technology
    Techno Press  2020
    Shear connectors are essential elements in the design of steel-concrete composite systems. These connectors are utilized to prevent the occurrence of potential slips at the interface of steel and concrete. The two types of shear connectors which have been recently employed in construction projects are C- and L-shaped connectors. In the current study, the behavior of C and L-shaped angle shear connectors is investigated experimentally. For this purpose, eight push-out tests were composed and subjected to monotonic loading. The load-slip curves and failure modes have been determined. Also, the shear strength of the connectors has been compared with previously developed relationships. Two... 

    Reinforced concrete beams without stirrups considering shear friction and fracture mechanics

    , Article Canadian Journal of Civil Engineering ; Volume 33, Issue 2 , 2006 , Pages 161-168 ; 03151468 (ISSN) Kazemi, M. T ; Broujerdian, V ; Sharif University of Technology
    A new expression for the shear capacity of reinforced concrete beams without stirrups was derived by calculating the aggregate interlock capacity across the major diagonal crack of the beam, a procedure somewhat similar to those based on the modified compression field theory. Two formulas were obtained from the simplification of this expression. All three relations capture the dependence of shear strength on the size of the beam, the ratio of shear span to beam depth, longitudinal reinforcement ratio, maximum aggregate size, and concrete strength. The limits of these formulas agree well with the limit solutions of shear failure load for very small and very large beams based on plastic and... 

    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... 

    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... 

    Endurance time method for multi-component analysis of steel elastic moment frames

    , Article Scientia Iranica ; Volume 18, Issue 2 A , 2011 , Pages 139-149 ; 10263098 (ISSN) Valamanesh, V ; Estekanchi, H. E ; Sharif University of Technology
    The Endurance Time (ET) method is a time history-based dynamic analysis procedure which uses special intensifying acceleration functions for evaluation of the seismic response of structures. One of the potential applications of the ET method is in the three-dimensional analysis of buildings under multidirectional excitations. In this paper, considering horizontal components of excitation, an algorithm for the multi-component analysis of building structures by the ET method is proposed, and results of the ET method for various steel moment frames with 1 to 7 stories are compared with results from time history analysis with real earthquakes. Results show that based on recommendations of... 

    Prediction of the penetrated rust into the microcracks of concrete caused by reinforcement corrosion

    , Article Applied Mathematical Modelling ; Volume 35, Issue 5 , 2011 , Pages 2529-2543 ; 0307904X (ISSN) Kiani, K ; Shodja, H. M ; Sharif University of Technology
    Consider a steel-rust-concrete composite consisting of a circular cylindrical concrete cover and a coaxial uniformly corroding steel reinforcement. Prediction of the amount of rust penetrated into the microcracks of concrete cover from a set of data measured at the surface of the concrete is of particular interest. The steel is assumed to be linear isotropic and rust follows a power law stress-strain relation. For the concrete, anisotropic behavior and post-cracking softening model is employed. The formulations lead to a nonlinear boundary value problem which is solved analytically. A key parameter β, defined as the ratio of the volume of corrosion products inside the cracks to the volume of... 

    Compactness requirements of RBS connections

    , Article Advances and Trends in Structural Engineering, Mechanics and Computation - Proceedings of the 4th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2010, 6 September 2010 through 8 September 2010 ; 2010 , Pages 663-666 ; 9780415584722 (ISBN) Vasseghi, A ; Shahidi, S. G ; Zingoni A ; Sharif University of Technology
    Flexible steel frame system is the most common structural system for mid-rise buildings. Northridge earthquake is turning point in designing flexible steel frames and their connections. During this earthquake a large number of beam-column connections in such structures were ruptured in a brittle manner. After this earthquake many researches were conducted on a variety of beam-column connections with an aim of improving their behavior during earthquake. One such connection which have been studied extensively both experimentally and analytically is a connection with Reduced Beam Section (RBS). The most important advantage of this connection is its high ductility and its ability to dissipate... 

    Behavior of polymer concrete beam/pile confined with CFRP sleeves

    , Article Mechanics of Advanced Materials and Structures ; 2017 , Pages 1-8 ; 15376494 (ISSN) Toufigh, V ; Toufigh, V ; Saadatmanesh, H ; Ahmari, S ; Kabiri, E ; Sharif University of Technology
    This research investigates the flexural behavior of a polymer concrete beam/pile encased with carbon fiber sleeve. The mechanical properties of carbon fiber sleeves in tension and cement and polymer concrete in compression were determined. Polymer concrete beams were tested in flexure to determine the bending moment capacity. Then, the test results were compared to the theoretical model results. Finally, a parametric study was conducted to determine the influence of beam/pile parameters on the capacity of the element. Based on the investigation, carbon fiber sleeve filled with polymer concrete exhibits outstanding structural performance including ductility and bending capacity. © 2017 Taylor... 

    Extrinsically enriched element free Galerkin method for heat and fluid flow in deformable porous media involving weak and strong discontinuities

    , Article Computers and Geotechnics ; Volume 103 , 2018 , Pages 179-192 ; 0266352X (ISSN) Iranmanesh, M. A ; Pak, A ; Sharif University of Technology
    Elsevier Ltd  2018
    In this study, an extrinsically enriched element free Galerkin (EFG) method is proposed for the thermo-hydro-mechanical simulation of saturated porous media. By taking advantage of partition of unity property of moving least square shape functions, weak discontinuities such as material interfaces are modeled using the Ridge enrichment function and impermeable strong discontinuities are simulated using the Heaviside function. Some guidelines are proposed for the selection of EFG numerical parameters to ensure the stability and accuracy of the results. Numerical examples are provided to illustrate the capability of the proposed approach for fully coupled THM analysis of discontinuous porous...