Resiliency Analysis of Bridge Systems Concerning the Performance-based Probabilistic Flood Loading

Abstract

Flood-induced loading is a significant hazard for bridge infrastructure, yet most design provisions lack explicit consideration of probabilistic flood demands. This study develops a performance-based framework that integrates hydrodynamic modeling, finite element analysis (FEM), reliability assessment, and fragility analysis to evaluate bridge resiliency under various conditions. Reinforced concrete highway bridge piers are modeled under variable flood intensities, incorporating combined hydrostatic and wave-induced pressures. Nonlinear FEM simulations provide damage indices for Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP), from which reliability indices and failure probabilities are derived. The main contributions are: (1) creation of benchmark bridge models coupling realistic flood hazard simulation with detailed structural response; (2) a flood-specific reliability framework calibrated to distinct limit states; (3) generation of fragility curves for piers under combined hydraulic loading; and (4) design-oriented recommendations for integrating flood hazards into load combinations. Results indicate that omitting flood effects in design leads to a significant underestimation of vulnerability. The fragility curves quantify the probability of exceeding each damage state across a range of intensities, revealing critical performance thresholds. This framework enables risk-informed, resilience-focused design and supports code development for infrastructure in flood-prone regions.