Residual displacement ground-motion model

Abstract

Residual displacement (RD), indicative of permanent post-earthquake deformation resulting from nonlinear structural response, plays an important role in assessing structural integrity and seismic safety. This study introduces a ground-motion model (GMM) for predicting RDs in inelastic single-degree-of-freedom systems, utilizing a large database of recorded ground motions. The RD GMM adopts key input parameters including 5%-damped elastic pseudo-spectral acceleration (PSA) over periods from 0.01 to 4.0 s, yield strength coefficient (Cy), earthquake magnitude (M), and closest distance to the fault rupture plane (Rrup). Levels of inelasticity are accounted for by employing the yield strength reduction factor, denoted as (PSA/g)/Cy. The results indicate that while M and Rrup significantly affect RDs, site class and significant duration have relatively less influence. RD GMM coefficients and unconditional standard deviations of the model are provided for specific Cy values across a period range of 0.01–4.0 s. The analyses indicate relatively large standard deviations in the GMM due to inherent variability in residual displacement, highlighting the importance of understanding and accounting for this variability in seismic design and performance assessment. Validation against a multi-degree-of-freedom bridge residual drifts demonstrates the effectiveness of the model in predicting the distribution of residual drifts.