Site Effects in Structural Response Predictions of Inelastic SDOF Oscillators

We study how the inelastic structural response predicted via synthetic seismograms is affected by the selection of site response models in ground motion simulations. We first generate synthetics for multiple scenarios and site conditions in Southern California using attenuation relations, site specific linear, viscoelastic and nonlinear analyses, and estimate the ground motion variability that results from the soil model selection. We next use bilinear single degree-of-freedom oscillators to demonstrate how this variability propagates to the inelastic structural response predictions. Results show high bias and scatter of the inelastic displacement ratio predicted using the empirical and linear elastic site response models relative to the nonlinear, for periods close to the fundamental period of the site. For the synthetic motions and sites used, we derive empirical correlations between the amount of bias and period range where it manifests, and selected input motion and site parameters.