GIRS-2025-04: New Near-Fault Adjustment Factors for Caltrans Seismic Design Criteria (SDC)

By: Silvia Mazzoni, Esra Zengin, Mahdi Bahrampouri, and Yousef Bozorgnia
DOI: 10.34948/N3S88X

ABSTRACT: This report covers analyses of Caltrans’ near-fault adjustment factors as recommended in the Caltrans Seismic Design Criteria. The report has two large chapters. Chapter 1 builds on prior the University of California Los Angeles studies that performed probabilistic seismic hazard analyses at numerous California sites across a range of return periods and multiple site classes. Using that dataset, the chapter develops simplified, distance- and period-dependent models that quantify directivity amplification of elastic response spectra statewide. Because many bridges are expected to respond inelastically during major earthquakes, the models are further adapted to capture period elongation consistent with typical bridge ductility demands. 

(full abstract available in the report)