Fragility Analysis of Deteriorating Bridge Components Subjected to Simulated Ground-Motion Sequences

This study assesses the impact of corrosion deterioration on the seismic performance of bridge components during a sequence of ground motions. Specifically, a simplified methodology is proposed to derive state-dependent fragility relationships for bridge components (i.e., relationships that explicitly depend on the damage state achieved by the component during a first shock) subjected to chloride-induced corrosion deterioration and simulated ground-motion sequences. Specifically, vector-valued probabilistic seismic demand models are derived for various corrosion levels. Those models relate the dissipated hysteretic energy in the sequence to a deformation-based engineering demand parameter induced by the first shock and a ground-motion intensity measure of the second shock, calibrated via sequential cloud-based time-history analyses. For each corrosion level, fragility relationships are first derived for a single ground motion; state-dependent fragility relationships are then derived by considering the additional damage induced by a second ground motion within the simulated sequence (structure-specific damage states are considered). Finally, continuous functional models are developed from the analysis results to assemble fragility relationships at a given corrosion level. The results demonstrate the significant impact of environmental deterioration in seismic-prone regions, emphasising the necessity of accounting for deteriorating effects in current practice.