Fragility Functions for Bridges in Liquefaction-Induced Lateral Spreads

Abstract

Fragility functions are generated for bridges in liquefied and laterally spreading ground using equivalent static global nonlinear finite element analyses. Bridges are classified based on structural configurations and vintage. Probability density functions are assigned to both structural and geotechnical properties of bridges. Nonlinear equivalent static analyses are conducted with inputs sampled randomly using the Monte Carlo simulation method. Cumulative distribution functions are fitted to the simulated data, and define the probability of exceeding various engineering demand parameters (pier column curvature ductility, pile cap displacement, abutment displacement, etc.) conditioned on the maximum free-field lateral spreading ground surface displacement. Correlations among EDPs are presented to facilitate risk assessment based on a vector of EDPs. The derived fragility functions, combined with seismic hazard analysis, liquefaction potential, and lateral spreading estimation, are useful in the context of performance-based earthquake engineering and risk assessment of current bridge inventory in California.