Seismic Evaluation of a Concrete Structure with Various Percentage of Symmetry in Accordance with Performance-Based Design

Abstract eng:
Because of shortcoming in the current building codes with respect to predicting the performance of concrete structures to earthquakes, in recent years, performance-based design or capacity spectrum method has received attention by researches and new codes. The purpose is to design a structure with predictable performance for different types of earthquake, so that the performance of the structure can be chosen on the basis of its purpose. In seismic evaluation of a concrete structure, its behavior, particularly plastic behavior in the effect of earthquake, is studied. For this purpose, seismic requirement parameter is compared to the capacity parameter of the structure. In the capacity spectrum method, it is necessary to determine of performance purpose of the structure, the Capacity Curve of the structure, and the performance point of the structure. In this article, 3D analyzes, and nonlinear and push-over design and analysis is performed for a concrete building with various percentages of symmetry. The performance purposes of the structure will be studied by performing of these analyzes and drawing the capacity spectrum of the structure, together with capacity curves for individual members. In this article, five-storey concrete buildings with storey heights of 3 meters are designed, which have three spans in Y direction and five span in X direction, with a size of 5 m, in an area with highly earthquake risk with a type II soil, according to ABA and 2800 code (Iran codes), as a intermediate bending frame with shear walls. The design is performed for two cases: symmetrical and unsymmetrical. The eccentricity is applied by moving shear walls, and is defined with various models with type of eccentricity percentages. After that the models are designed and their structural details are obtained in accordance with ABA code (Iran code) (for structures with intermediate bending frames), the bending and shear joints, along with the interaction of bending and axial force diagrams must be extracted for various elements (beams, columns, walls) from ATC and FEMA codes, and applied to individual elements for nonlinear analyses were performed on the structure by using ETABS and SAP software, in order to obtain a seismic evaluation for nonlinear static and nonlinear dynamic analysis. In all models, whether symmetrical or nonsymmetrical, the nonlinear static analysis results are in good conformity with the nonlinear dynamic results. Nonlinear dynamic analyses show that selection of accelerometers and their scaling (calibration) has a considerable effect on the response of the structure.

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