Assessment of Seismic Performance of Buildings with Incorporation of Aftershocks

Aftershock ground motions are essential for the study of aftershock synthesis into seismic risk. However, the number of available aftershock records is limited, which necessitates that the methods for synthesizing aftershocks to be developed. This paper aims to propose a methodology to synthesize aftershocks based on the information of the mainshocks, which is able to incorporate the uncertainties of ground motions and can be utilized in seismic risk analysis. The proposed method is illustrated by application to risk analysis for two nonductile RC frame buildings and is validated by comparing with the results obtained from using as-recorded mainshock-aftershock (MS-AS) sequences. The results calculated when only mainshocks are considered are also studied to investigate the MS-AS effects. The paper shows that the synthesized MS-AS sequences using the proposed method can yield results statistically close to the as-recorded sequences. The results also reveal that only considering the mainshock will underestimate the seismic risk but the underestimation is limited.