Peak ductility demand of mainshock-aftershock sequences for Japanese earthquakes

A large mainshock triggers numerous aftershocks. Large aftershocks can cause additional damage and disruption to buildings and infrastructure in a post-disaster situation. This study investigates the effects of aftershocks on peak ductility demand of elastic-perfectly-plastic single-degree-of-freedom systems using real as well as artificial mainshock-aftershock sequences. First, empirical assessment of the incremental peak nonlinear response due to aftershocks is conducted by using real mainshock-aftershock sequences constructed from the K-NET and KiK-net databases for Japanese earthquakes. Subsequently, an alternative method of generating artificial time-history data of mainshock-aftershock sequences is implemented based on the generalized Omori’s law and suitable record selection criteria for aftershocks. Analysis results indicate that overall increase of the peak ductility demand ranges from 5% to 20%, depending on the vibration period of a structural system and seismic excitation level, and that peak ductility demands for real and artificial sequences are similar and thus artificial sequences can be substituted for real sequences.