Evaluation of the usage ratio graphs and energy dissipation in concrete structures with shear walls, under different earthquake records

Abstract

A. Ahmadi, F. Haghighatbin

Usage Ratio Graphs are used as a tool to assess whether a structure meets performance criteria. As the load factor increases in a gravitational analysis, the relative displacement increases in an Push-Over analysis, or the time increases in a dynamic analysis, the usage graphs show the changes in the usage ratio in accordance with the increment in the load factor, relative displacement or time, respectively depending on the type of the analysis. The responses of a structure under an earthquake can depend on the amount of energy dissipation by the structure. In an analysis of elastic structures, it is generally assumed that energy is dissipated by the viscous damping (this is presented by approximation in modeling, Except for structures that really use viscose dampers). In other hand for the inelastic structures analysis, it is also commonly assumed that in addition with the viscous damping the excess energy is dissipated by inelastic effects (inelastic deformation, failure, etc.). Energy graphs determine which members in the structures have a greater share in inelastic energy dissipation. These graphs help to better estimate the structure's performance. In this study, four “moment frame” concrete structures with irregular planes and moderate ductility and with reinforced concrete shear walls, were analyzed. The Structures are designed in two different shear wall plan configuration, with 8 and 12 stories. The static and dynamic nonlinear analysis of the structures were carried out using the “Perform-3D v5.0” software, which is one of the most powerful tools in the field of nonlinear analysis of structures under earthquake loads.

Keywords: Concrete structures; shear walls; irregular plan; nonlinear dynamic analysis; dissipated energy; usage graph

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