Criteria for suppression of deformation concentration of building frames under severe earthquakes

摘要

It has been revealed by symmetry limit theory that an unknown type of collapse behavior, characterized by cyclic growth of a bow shaped mode overall deflection, could occur in a multistory multi- bay weak-beam planar frame subjected to a static cyclic program of top horizontal displacement. Dynamic response analysis of the multistory frame, performed later, has shown that the bow-shaped mode deflection is possible to appear in a restricted lower part of the frame and, thereby, deformation concentration occurs in that part in the process of dynamic collapse. In this paper, criteria for suppression of growth of the bow-shaped mode deflection and the deformation concentration will be proposed. Even if a frame is designed so that the criteria are satisfied, a gradual one-way drift of the sway-mode vibration center may still be observed under a cyclic ground motion. Criteria for suppression of the sway drift will also be proposed to meet higher-level safety requirements.