Comparison of dynamic response of isolated and non-isolated continuous girder bridges subjected to near-fault ground motions

The dynamic response of seismic isolated continuous girder bridges subjected to either near-fault or far-field ground motions is compared to the non-isolated ones. Near-fault earthquake ground motion data are collected from the 1999 Taiwan Chi-Chi earthquake. The earthquake data recorded at the same sites from other events serve as far-field ground motions. Typical three-span continuous concrete box girder bridges designed under Taiwan seismic design specifications of highway bridges are adopted for this study. These bridges are assumed straight, founded on rigid rock and only the longitudinal response is considered. Parametric studies for the dynamic responses of isolated bridges by input near-fault ground motions are developed. The PGV/PGA value of near-fault earthquake records is identified as the key parameter governing the bridge response.