Fragility curves for bridges under differential support motions

This paper employs the notion of fragility to investigate the seismic vulnerability of bridges subjected to spatially varying support motions. Fragility curves are developed for four highway bridges in California with vastly different structural characteristics. The input in this analysis consists of simulated ground motion arrays with temporal and spectral nonstationarities, and consistent with prescribed spatial variation patterns.

Structural damage is quantified through displacement ductility demands obtained from nonlinear time-history analysis. The potential use of the ‘equal displacement’ rule to approximately evaluate displacement demands from analysis of the equivalent linear systems is examined.