جستجوی مقالات مرتبط با کلیدواژه "دیوار برشی بتن آرمه" در نشریات گروه "عمران"

Reinforced-Concrete Shear Wall (RCSW) is a common lateral resisting system especially in mid and high-rise structures. This popularity among engineers is due to high ductility and in-plane stiffness of the RCSWs. RCSWs have shown good performance as seismic load-bearing systems in past earthquakes. However, the main disadvantage of RCSWs is the crushing of concrete at the foot of the wall and as a result the buckling of the reinforcement in this area, which makes it difficult and, in some cases, impossible to repair after the earthquake. As a solution, using Buckling-Restrained Brace (BRB) as boundary elements at the base of the RCSWs is proposed and investigated in this research. For this purpose, two sets of 6 and 12-storey structures with conventional RCSW and BRB-RCSW as lateral resisting system were designed, and their seismic response were assessed through static (monotonic and cyclic), dynamic Nonlinear Time History (NLTH) and Incremental Nonlinear Dynamic Analyses (NIDA). The results indicate improved structural performance and an increase of response modification factor from 4.4 in conventional RCSW to 5.47 in RCSW-BRB. Furthermore, the proposed system prevents the induced damage at the foot of the RCSW while the replaceable BRBs act as the fuses, increasing the resiliency of the structure. So that the behavior factor of the frame equipped with buckling-restrained braces increased by 30 percent in the 6-story building and 20 percent in the 12-story building.

In most seismic design codes, lateral loads are reduced by applying the response modification coefficient in the linear static analyses. Hence, the lateral displacements of the structure should be increased to obtain a realistic estimation of the actual displacements. In this regard, static drifts are multiplied by a deflection amplification factor (Cd). This factor is proposed based on single earthquakes in seismic codes such as ASCE 7 and Standard No. 2800 (4th Edition) while structures in seismic regions will typically be exposed to a number of aftershocks after a major earthquake. Since, the repair of the structures will not be practically possible before exposing to aftershocks, ensuring the proper performance of structures under successive earthquakes is essential. Accordingly, in this paper, deflection amplification factor has been evaluated for dual system of special moment-resisting frame with shear wall under critical seismic sequences. For this purpose, 3 RC building frames with the number of 3, 7 and 11 story have been subjected to linear static, linear and nonlinear dynamic analyses and the deflection amplification factor has been calculated and extracted for each of them under two states of successive and single earthquakes. The results show that successive shocks do not significantly affect the Cd compared to a single earthquake. In addition, a supplementary study has been performed for a number of single earthquakes (near-fault earthquakes which have been introduced in FEMA P695) to provide more reliable results. This investigation reveals that the proposed values in ASCE7-16 and Standard 2800 are not sufficient for Cd coefficient.

In recent years, reinforced concrete (RC) shear walls have been welcomed by structural designers with regard to their desirable seismic performance in terms of ductility. Most of the time, creating an opening in the RC shear wall due to the architectural issues, which is inevitable, results in reducing the strength, ductility and stiffness of the wall.For this reason, the issue of retrofitting the RC shear walls is developed to solve these weaknesses. In this paper, an RC shear wall with opening was retrofitted with eight different schemes of carbon fiber reinforced polymer (CFRP) sheets in ABAQUS software which were:1-vertical and horizontal CFRP sheets around the opening in RCSW1 sample, 2-horizontal CFRP sheets to increase the shear capacity in RCSW2 sample, 3- vertical and oblique CFRP sheets to prevent diagonal cracks in RCSW3 sample,4-horizontal and vertical sheets in corners of the opening in RCSW4 sample,5-horizontal and oblique CFRP sheets to reduce diagonal cracks and the strain at the foot of the wall in RCSW5 sample, 6-vertical CFRP sheets to increase flexural capacity in RCSW6 sample,7-vertical, horizontal and diagonal CFRP sheets in RCSW7 sample, and 8- horizontal and vertical CFRP sheets in whole of the wall to increase flexural and shear capacity and improve ductility in RCSW8 sample. All samples were subjected to cyclic lateral loading.Various parameters such as stiffness, displacement, ductility and failure were selected to evaluate the results.Results showed that the RCSW8 in comparison to the control sample had a 12% increase in the bearing capacity.

Structural walls are widely used in building structures as the major structural members to provide substantial lateral strength, stiffness and the inelastic deformation capacity needed to withstand earthquake ground motions. In this article the behavior of composite shear walls with continuous boundary elements are compared and contrasted with a state in which the wall’s boundary elements are discontinuous and interrupted and the boundary steel columns are connected to the foundation through the column’s baseplate and bolts; and these are all to assess and appraise some hypotheses by the structural designers in designing these walls. The finite element software is first calibrated and the accuracy of its results is validated through modeling the experimental samples. In this research, the concrete’s nonlinear finite element analysis method and concrete damage plasticity model have been used for the concrete’s behavior modeling. The results of this study indicate that the wall boundary elements’ continuity improve the composite shear walls’ behavior. Meanwhile, this effect increases by an increase in the number of the wall’s floors.

Composite construction in steel and concrete offers significant advantages for use as the primary lateral resistance systems in building structures subjected to seismic loading. While composite construction has been common for over half a century through the use of composite beam and joist floor systems, over the past decade a substantial amount of research has been conducted worldwide on a wide range of composite lateral resistance systems. These systems include unbraced moment frames consisting of steel girders with concrete-filled steel tube (CFT) or steel reinforced concrete (i.e., encased steel sections, or SRC) beam-columns; braced frames having concrete-filled steel tube columns; and a variety of composite and hybrid wall systems.
Structural walls are widely used in building structures as the major structural members to provide substantial lateral strength, stiffness, and the inelastic deformation capacity needed to withstand earthquake ground motions. In recent years, steel reinforced concrete (SRC) walls have gained popularity for use in high-rise buildings in regions of high seismicity. SRC walls have additional structural steel embedded in the boundary elements of the reinforced concrete (RC) walls. Walls with additional shapes referred as composite steel-concrete shear walls, contain one or more encased steel shapes, usually located at the ends of the wall.
Composite shear walls with steel boundary element are known as the structural members able to withstand high in-plane lateral forces at low displacement levels. Reinforced concrete shear walls with steel boundary element being performed in Iran are joined to the foundation, in boundary element section, usually through bolts and base plates. Most reliable codes of the world have nothing to say about the behavior of this type of shear walls, and no experimental studies or analyses have been conducted on the behavior of this type of shear walls. In the past decade, great effort has been devoted to the study of seismic behavior of SRC walls, for Design provisions for SRC walls have also been included in some leading design codes and specifications, for example, AISC 341-10 , Eurocode 8, and JGJ 3-2010
Exposed baseplates together with anchor bolts are the customary method of connection of steel structures to the concrete footings . In this paper, the influence of cross section of base plate’s joint bolts to the foundation and the wall’s longitudinal bars embedding within the area of boundary element in the foundation, on the behavior of this type of shear walls have been investigated. The finite element software is first calibrated and the accuracy of its results is validated through modeling the experimental samples. In this research, the concrete’s nonlinear finite element analysis method and concrete damage plasticity model have been used for the concrete’s behavior modeling. The results show that increasing in the level of bolt’s cross section and also the embedding of longitudinal bars of boundary element in the foundation cause an improvement of the capacity of these walls. However, these walls’ resistance against the normal axial loads is considered to be less than reinforced concrete shear wall.

Concrete shear walls are the most commonly used systems to resist lateral loads due to earthquakes in high rise buildings. In recent years، seismic design methodologies have put more attention on limiting the maximum drift experienced by a structure during earthquake. Very large in-plane stiffness of shear walls and its role on redistribution of the lateral loads from columns to wall provide an excellent drift control. Nevertheless، Time expiring، structural damages and early code shortcomings cause unsuitable efficiency of existing structural walls against earthquake. Fiber Reinforced Polymer (FRP) materials have greatly used in strengthening and retrofitting of structural elements in recent years. The excellent features of FRP materials set them the first alternative in the strengthening projects. However، a glance on the previous studies shows that very limited analytical and/or experimental studies have been conducted on the FRP strengthening of the slender RC shear walls so far. In this paper، effect of FRP confinement of boundary elements in slender RC shear walls on the overall behavior of boundary elements is investigated. The finite element software is calibrated and verified using available experimental data. Nonlinear finite element analysis of reinforced concrete walls is performed using damage plasticity model and tension stiffening effects. Results of the current study show the superior effectiveness of strengthening FRP composite layers on ductile behavior of concrete shear walls

Concrete shear walls are the most common system resisting against seismic loads in the world. These elements carry the lateral loads by a combination of the axial, shear and flexural responses. Change in the seismic code requirements, subjecting intensive dynamic loads such as explosion or earthquake and other destructive effects make the shear walls weak for continuing service life. In the recent years FRP materials have attracted much interest. FRP application in retrofitting projects is appealing because of their unique properties. Nevertheless, a review on the previous studies shows that despite the squat walls, very limited analytical and/or experimental studies have been conducted on the FRP strengthening of the slender RC shear walls under monotonic loading so far. In this paper it is focused on the strengthening of boundary elements with FRP and it’s effect on the wall behavior. The finite element software is calibrated and verified using available experimental data. Nonlinear finite element analysis of reinforced concrete walls is performed using damage plasticity model and tension stiffening effects. Results of the current study show the superior effectiveness of strengthening FRP composite layers on the behavior of the concrete shear walls.

One of the methods for seismic retrofit of mid-rise buildings is the use of dual systems such as moment resisting frame accompanied with another lateral load carrying system such as steel bracing frame or reinforced concrete shear wall. The selection of shear wall or steel braced frame is one of the most important matters. Therefore, investigation of the behavior in these structures and knowing the effect of those two systems must be considered in coupling with moment resisting frame system. In this study, the effect of shear wall and steel braced frame in the behavior of structure and the dual system interaction is investigated by the analysis of steel moment resisting frame in a 0 story building using ETABS 000 software. The analytical result show that shear wall have more lateral stiffness than X-braced system and more logical when considered from executive point of view. For controlling the lateral deformation of structures the analytical results show that the increase in cross sectional area of steel braces have a limited effect on the response, but increasing the number of braced bays is more effective.