Collapse Behavior and Ultimate Earthquake Resistance of Weak Column Type Multi-Story Steel Frame with RHS Columns

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-Ä 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. In the analysis, realistic hysteresis model of story including deteriorating range is used. From analytical results, collapse behavior and ultimate earthquake resistance of steel frames governed by deterioration of columns are evaluated.