PEER has published Report No. 2024/09: "Correlation of Ground Motion Duration with Spectral Acceleration and Implications for Expected Bridge Performance." It was authored by Maria Camila Lopez Ruiz and Tracy Becker, Department of Civil and Environmental Engineering, University of California, Berkeley; Micaela Largent and Jennie Watson-Lamprey, Slate Geotechnical Consultants, Inc.
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Abstract
Construction or detailed evaluation of transportation infrastructure requires site-specific ground motions for input into nonlinear structural models. These site-specific ground motions are generally selected based on the magnitude, distance, and site condition of the recorded ground motion. A preliminary study performed by Slate Geotechnical Consultants found that duration and spectral acceleration are negatively correlated for large-magnitude earthquakes recorded on soft-soil sites (Vs30<360 m/s). This means that if the target spectral acceleration is above average, then the average duration associated with that ground motion should be below average for the scenario magnitude and distance. This ground motion duration correlation implies that the current state of the practice is overestimating the probability of collapse for structures. This project aims to improve the characterization of ground motion duration and evaluate how the improved characterization affects bridge fragilities used in the Performance-Based Earthquake Engineering (PBEE) framework. Numerical models for two prototype structures, a major toll bridge and a typical highway overpass, are developed using OpenSees. Using these models, the effect of ground motion duration is evaluated quantitatively following the PEER PBEE methodology.