Collapse Capacity of Inelastic Single-Degree-of-Freedom Systems Subjected to Mainshock-Aftershock Earthquake Sequences

This study investigated the collapse capacity of inelastic single-degree-of-freedom (SDOF) systems subjected to mainshock-aftershock earthquake sequences. A hysteretic model incorporating strength and stiffness deterioration was used to describe the inelastic behaviors of SDOF systems under seismic excitations. An ATC63 far-field record set was adopted as seed mainshock records to synthesize earthquake sequences. An extended IDA method was employed to calculate the collapse capacity of inelastic SDOF systems subjected to mainshock-aftershock earthquake sequences by scaling the earthquake sequence as a whole. An extensive parametric study was conducted for examining the effects of hysteretic model parameters and artificial earthquake sequences synthesized by different methods and with near-field and far-field mainshock earthquakes on system collapse capacity. Through comparing the collapse capacity for mainshock-aftershock earthquake sequences and that for mainshock earthquakes only, it is found that aftershocks can yield a significant reduction on the median collapse capacity for all systems and lead to an important increase on the dispersion of collapse capacity for the systems at most periods. Based on the parametric study results, empirical expressions were proposed to predict the aftershock-induced reduction and increase on the median and dispersion of collapse capacity, respectively.