Permissible Scale Factors for Various Intensity Measures in Aftershock Ground Motion Scaling

This manuscript investigates the bias introduced by scaling aftershock ground motions when evaluating the performance of structures subjected to earthquake sequences. The study focuses on different hysteretic behaviors exhibited by structures and selects eight intensity measures as scale indicators. A benchmark database comprising 274 recorded mainshock-aftershock ground motions is utilized for analysis. The findings reveal that scaling aftershock records using intensity measures such as SI (seismic intensity), PGV (peak ground velocity), IC (Arias intensity), and Sa (spectral acceleration) relative to mainshock records effectively controls the mean bias within 30% throughout the entire period range, given a maximum scale factor of 10.0. However, it is observed that the additional damage in systems exhibiting un-degrading hysteretic behavior is more significantly affected by aftershock ground motion scaling compared to systems with degrading hysteretic behavior. Furthermore, scaling aftershock ground motions upwards using relative Sa tends to overestimate the additional damage incurred by structures. These results emphasize the importance of considering the specific hysteretic behavior of structures when applying aftershock ground motion scaling, as well as selecting appropriate intensity measures for accurate evaluation of structural performance.

Automated summary

This manuscript investigates the bias introduced by scaling aftershock ground motions in evaluating the performance of structures subjected to earthquake sequences. The study reveals that scaling methods using certain intensity measures effectively control the mean bias within 30% throughout the entire period range. However, the additional damage in systems with different hysteretic behaviors is significantly affected by aftershock ground motion scaling, and scaling upwards tends to overestimate the additional damage incurred by structures. These results emphasize the importance of considering the specific hysteretic behavior of structures and selecting appropriate intensity measures for accurate evaluation of structural performance when applying aftershock ground motion scaling.