Nonlinear dynamic analysis and seismic fragility assessment of a corrosion damaged integral bridge

A 3D nonlinear finite element model is developed for a multi-span integral bridge with corroded reinforced concrete (RC) piers. Through a series of nonlinear dynamic time-history analyses the impact of corrosion on the seismic performance of this aging bridge is explored. To model the uncertainties associated with the material properties and corrosion models, a Monte Carlo Simulation with Latin Hypercube Sampling method is employed. A new phenomenological hysteretic model for corroded reinforcing steel is used. This model is able to simulate the combined effect of geometrical nonlinearity due to inelastic buckling of reinforcement and material nonlinearity due to yielding of material and low-cycle fatigue degradation under cyclic loading. Moreover the effect of corrosion damage on cracked cover concrete due to corrosion of vertical bars and damaged confined concrete due to corrosion of horizontal tie reinforcement are also included in the model. This study evaluates the impact of chloride induced corrosion of the RC columns on the seismic fragility of the bridge. Fragility curves are developed at a various time intervals over the lifetime. The results of this study show that the bridge fragility increases significantly with corrosion.