Seismic collapse resistance of RC frame structures——Case studies on seismic damages of several RC frame structures under extreme ground motion in Wenchuan Earthquake

The seismic damage of several groups of RC frames in the hardest-hit zone of the Great Wenchuan Earthquake is introduced.In each group,some frames collapsed while others survived,despite that they had similar site condition.The collapse resistance of two typical frames in earthquake is analyzed with elastic-plastic time-history analysis,pushover analysis and collapse margin ratio(CMR) analysis which is based on incremental dynamic analysis(IDA).The corresponding collapse resistance research and calculation methods in foreign countries are introduced.The main influencing factors and the evaluation indices that control the structural collapse resistance,as well as the global redundancy and integrity,are discussed.Based on this study,the following methods are identified to be effective in improving the collapse resistance of frames:(1)guarantee the global loading resistance capacity and lateral deformation capacity;(2)increase the redundancy and integrity;(3)achieve rational yield mechanism with proposed engineering method;(4)buildup dual-system for frame structures with infill walls.Finally,the problems that may need further research on structural collapse are proposed.