Inelastic Responses of Two-Way Asymmetric-Plan Structures under Bidirectional Ground Excitations-Part II: Response Spectra

Abstract

Based on the studies in the companion paper, this paper presents the inelastic response spectra for asymmetrical structures (SAS) under bidirectional ground excitations. Firstly, the constant-strength SAS were constructed and compared with the corresponding conventional constant-strength response spectra. It was found that the modal ductility demands of an asymmetric-plan structure could be significantly overestimated from the conventional constant-strength response spectra as the nonlinear "modal" rotation and translations may not be proportional. Furthermore, the translation-rotation interaction effect is not considered in the conventional constant-strength response spectra. Secondly, the influences of the three-degree-of-freedom (3DOF) modal parameters on the ductility demand were extensively studied. Thirdly, the normalized peak edge translation spectra were also investigated. It was found that the normalized peak edge translation resulting from a single vibration mode may be overestimated twofold by using the single-degree-of-freedom (SDOF) modal systems. © 2012, Earthquake Engineering Research Institute.