ASSESSMENT ON ASEISMIC PERFORMANCE OF REGULAR STRUCTURES BY IMPROVED CAPACITY SPECTRUM METHOD

The usual capacity spectrum method of structural seismic performance evaluation can only consider the first response mode of structures,and the influence of high modes can not be taken into account,so the error is introduced.A new type of equivalent single-degree-of-freedom(SDOF) is set up using the equivalent mode and equivalent mode participation coefficient.Then the capacity spectrum method is used to evaluate the seismic performance of structures.The method can avoid the nonlinear dynamic time-history analysis,and can get more seismic information on structures comparing with the latter.The example analysis shows that the high modes have little influence on the structural response in the elastic stage but have major influence in the inelastic stage,and the example also shows that the response obtained using the usual capacity method is smaller than the actual response of structures,so it biases toward the insecurity,while the rational result can be got by the improved capacity spectrum method aseismic.