Behavior assessment of common shear walls in iran with steel boundary element

Abstract:
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.

Keywords: Reinforced concrete shear wall, Steel boundary element, Concrete damage plasticity model, Finite element model.