Performance evaluation of precast frames using CSM-based fragility analysis

Seismic performance evaluation of precast building frames is of great importance because precast buildings have failed during earthquakes in the past. The present work evaluates the seismic performance of a 10-story precast building frame using pushover analysis (POA). Three types of precast connections are incorporated in the study, and the corresponding monolithic connections in the frame are utilized to evaluate the relative performances of the precast frames. A pushover analysis is performed for frames with each type of connection, and three performance points (PP) are identified: one in the elastic range, the second in the elastoplastic range, and the third in the near collapse state. The PP is obtained using the average response spectrum of an ensemble of seven earthquake records belonging to three types of earthquakes: a far field, a near field with a directivity effect, and a near field with a fling step effect. At the PP, responses obtained from POA are compared with the average responses of the nonlinear time history analysis (NLTHA). The response quantities of interest include maximum base shear, maximum top displacement, and maximum inter-story drift ratio (MIDR). Additionally, performance evaluation includes the study of the characteristics of the fragility curves corresponding to four defined damage states similar to those defined by HAZUS for nonlinear static analysis. The fragility curves are developed based on peak ground acceleration (PGA). The results of the study indicate that depending on the performance points, a maximum of 30% difference in responses between POA and NLTHA is observed. Furthermore, the nature of the fragility curves of the precast and monolithic frame could be different in the higher damage state; however, the same may not be significant for the lower damage state.