Abstract
In seismic design, moment resisting frame is designed to form the overall sway mechanism under severe earthquake. However, it is possible to form the weak column mechanism with the rise of strength of beams and panel zone due to strain hardening. The causes to collapse the weak column type frame are strong bi-axial seismic force, P-Δ effect and deterioration of restoring force. In this study, a series of response analyses of weak column type multi story steel frames under bi-axial ground motion are carried out. At first, using the elasto-perfectly-plastic hysteresis model, influence of the bi-axial ground motion and P-Δ effect on collapse behavior of frames are evaluated. Moreover, using the realistic hysteresis model including deteriorating range, collapse behavior and ultimate earthquake resistance of frames governed by deterioration of columns are evaluated.
