Ground motion selection and modification evaluation for highway bridges subjected to Bi-directional horizontal excitation

Abstract

Reinforced concrete (RC) highway bridges are primary lifeline infrastructures where accurate seismic structural analysis is essential to ensure the safety of bridges. The nonlinear seismic behavior of bridge structures generally exhibits distinct differences in the longitudinal and transverse directions, and thus studies on bi-directional ground motion excitation are needed. Performance-based earthquake engineering (PBEE) methodology explicitly takes into account uncertainties in hazard, structural response, damage, and loss estimation such that enables a comprehensive understanding of the structural performance in a probabilistic manner. For a given large ground motion scenario, this study takes advantage of the PBEE methodology (the first two stages of hazard and structural response) to develop a benchmark probability distribution of the seismic demands (PDSD) for a given bridge structure considering different assumed intercept angles of the input ground motions with the bridge longitudinal axis. The accuracy and reliability of the PDSD estimates from various ground motion selection and modification procedures for the purpose of future bridge designs are evaluated against this reference benchmark PDSD. Such an evaluation is conducted for several engineering demand parameters of three representative RC bridges in California.