The Impact Of Higher Modes Yielding On Static Modal Pushover Analysis Procedure

Nonlinear static procedure for structural seismic performance evaluation has been introduced into Chinese Code for seismic design of buildings (GB50011-2001). In order to improve the accuracy and applicability of the method, many researchers have done a lot of research and improvements. For example, a modal pushover analysis procedure is proposed by Chopra considering the impact of higher vibration modes; Much improvement is made on modal pushover analysis procedure by Mao Jian Meng, who considered structural stiffness after the first mode yielding and used two-stage loading to the first mode . It is verified by one example that the improvement on modal pushover analysis has further improved the accuracy.The main problem in this paper is to discuss the impact of higher mode yielding on static modal pushover analysis procedure. In order to solve this problem, a multi-stage modal pushover analysis procedure is proposed. Based on this method, different stages loading mode are used in modal pushover analysis. The results of different stages loading mode will be compared to each other, and also to the time history result.The results of two examples with different heights show that, the impact of higher mode yielding should not be ignored in modal pushover analysis, and it's influence in the high-level structure is more significant than the multi-layer structure. Considering the yield of higher modes when it occurs would enable modal pushover analysis closer to time history analysis, which can further improve the computational accuracy of modal pushover analysis.The multi-stage modal pushover analysis procedure proposed, which according to the specific circumstances of the structure to determine whether higher modes yielding should be considered, is reasonable in theory. It is improved that the calculation results of the two examples by this method are closed to the time-history analysis results when higher mode yielding is reasonably considered. Meanwhile, the method does not increase too much work. It is suggested that the method can be applied to more seismic analysis for framework.