Effects of Number of Spectral Periods and Input Motion Screening Criteria on the Representative Motions for Charleston, SC

Abstract

In this study, the number of periods in acceleration response spectra and the characteristics of input motion and screening criteria on the representative earthquake time histories are investigated for the Charleston, SC, area. Uniform hazard spectra (UHS) obtained from probabilistic seismic hazard analysis (PSHA) and NEHRP provisions typically contain 10–22 spectral periods ranging from 0.01 to 10 s. Acceleration response spectra for recorded time histories generally have peaks and valleys between the spectral periods used for the UHS. To address this issue, the UHS was re-digitized by adding more spectral periods (50–300) using a linear interpolation technique in semi-log space. The seed time histories were selected from the NUREG/CR-6728 ground motion database and modified to match the re-digitized UHS using a time domain modification technique. The results showed that using re-digitized UHS for spectral matching minimizes the peaks and valleys. However, sensitivity analyses showed that the response spectra of the modified acceleration time history matched the UHS well when the number of re-digitization periods increased but resulted in a considerable distortion in the corresponding displacement time histories. The study provided insights into the effect of the number of spectral periods and criteria for screening seed time histories for spectral matching to generate site-representative time histories.