Seismic fragility assessment of corroded RC bridge piers using an energy-based damage index at different corrosion levels

This study develops an integrated framework comprising an energy-based damage index (IEBD) and seismic fragility analysis to assess the seismic performance of corroded reinforced concrete (RC) bridge columns with different concrete compressive strengths. The combined effects of rebar corrosion, concrete strength, and shaking intensity are evaluated through nonlinear incremental dynamic analysis using a database of far-field ground motions. IEBD is derived from the relationship between cumulative hysteretic energy dissipation and input energy to develop fragility curves for different damage states. The findings reveal significant damage progression and reduce seismic capacity of the RC bridge columns with increasing reinforcement corrosion. Similarly, increasing damage is associated with a reduction in the PGA required to reach a given damage level, indicating that as corrosion progresses, corroded columns can reach the same damage state under lower seismic intensities. Also, concrete compressive strength significantly influences the degree to which rebar corrosion affects structural performance. Higher concrete strength provides greater protection under less severe corrosion conditions but loses its beneficial effect as corrosion severity increases. Overall, the proposed framework provides a physically meaningful approach for probabilistic seismic vulnerability assessment and supports the evaluation of retrofit strategies for RC bridge piers.