Cyclic Pushover Method for Seismic Assessment Under Multiple Earthquakes

A new method for the seismic performance assessment of structures subjected to a sequence of earthquakes is presented. The method is based on the cyclic pushover analysis of a multi-degree-of-freedom (MDOF) structure. Instead of relying on a single value of target displacement, as in the case of monotonic pushover methods, a simplified cyclic displacement history is derived from an equivalent single-degree-of-freedom (SDOF) structure for the assessment of the MDOF one. The main advantage of the method is that it directly accounts for cyclic degradation of the actual MDOF system while retaining the simplicity and computational efficiency of SDOF systems for displacement demand evaluation, thus making it attractive for practical applications. The procedure is exemplified in detail using ductile and nonductile reinforced concrete (RC) frames as benchmark structures subjected to the Central Italy sequence. Further comparison with fully nonlinear time-history analysis and code-prescribed monotonic pushover is provided in order to assess the accuracy and advantages of the proposed method.