A Systematic Framework for the Seismic Risk Management of RC Bridges Using Various Retrofit Strategies

– Reinforced concrete (RC) bridges are vital components of the transportation infrastructure. However, several existing bridges may fail to meet the target performance objectives of current seismic design standards. Past earthquakes have underscored the vulnerability of substandard bridges to damage modes such as pounding and curvature ductility demands, emphasizing the critical need for seismic retrofitting. This paper proposes a systematic methodology for selecting individual and hybrid retrofit strategies for the seismic risk management of substandard RC bridges. This framework is applied to a benchmark multi-span RC bridge representing a large bridge inventory in a medium seismicity study region. The proposed framework selects retrofit measures that mitigate various damage modes, including excessive bearing displacement, pounding between nearby bridges, and significant curvature ductility demands in bridge bents. The adopted retrofit approaches are verified against previous experimental results through detailed three-dimensional fiber-based modeling and implemented in the representative bridge to evaluate the dynamic response behavior of the existing and retrofitted bridges. The nearby bridges' lateral capacity is initially investigated to assess the retrofit options by analyzing various local damage indicators. Fragility analyses are then performed under different seismic scenarios to compare the effectiveness of the proposed retrofit strategies. Finally, a versatile seismic performance-cost indicator is employed to prioritize the retrofit alternatives and to propose a hybrid retrofit strategy that effectively addresses various damage modes inherent in the substandard bridge and ensures the safety and serviceability of existing RC bridges.