Proper configuration of stiffness and strength centers in asymmetric single-story structures with semi-flexible diaphragms

Abstract

While plan-asymmetric structures have more potential for torsional effects and diaphragm flexibility during seismic response, they had received less attention from this viewpoint in previous studies. In fact, due to the complex torsional-flexibility interaction of asymmetric structures with flexible diaphragms when subjected to seismic responses, evaluating the performance of these structures is more complicated. Therefore, there is not a general agreement as what configuration of centers (stiffness and strength centers) is the best one to limit seismic demands in such structures. Accordingly, there is a need to conduct extensive parametric studies to quantify the effects of structural asymmetry, diaphragm flexibility and earthquake intensity simultaneously, so that designers can be aware of the likely impact of diaphragm flexibility in asymmetric-plan structures. For this purpose, single-story models with different configurations of mass, stiffness, and strength centers and a wide range of diaphragm flexibility from fully rigid to quite flexible were studied. Since ground motion characteristics have a great impact on the behavior of these structures, the considered models were subjected to a set of seismic ground motion records and each record was scaled to eight different earthquake intensities. Then, the seismic behavior of these models was evaluated using different structural response parameters: structural rotation, story drifts of lateral load resisting elements, diaphragmś deformational modes and sensitivity of the structural seismic behavior to earthquake intensity. Finally, based on the obtained results, the proper configuration of stiffness and strength centers in asymmetric structures with flexible diaphragms has been proposed.