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Abstract

An intended performance of a structure under different seismic hazard levels can be obtained by applying the performance-based seismic design (PBSD) approach. Various performance levels and the respective limit states need to be set for employing PBSD. These limit states corresponding to different performance levels are unavailable in the latest codes and guidelines for existing seismically deficient bridges. Being major components, multi-column bents have notable effects on the seismic behaviour of these bridges. Thus, a typical deficient bent is retrofitted with different alternatives such as carbon fibre-reinforced polymer (CFRP), steel, engineered cementitious composite (ECC), and concrete jackets, and the development of limit states for each alternative is sought in this research. Incremental dynamic analyses were performed to come up with the limit states expressed in terms of limiting drifts and damage indices for different performance levels of retrofitted bents. A detailed example has been developed to demonstrate a retrofit design for achieving the target seismic performance with the proposed damage states. Fragility analysis was conducted to achieve the conditional probabilities of exceeding various damage states at different hazard levels under various earthquake scenarios. The effects of various performance-based damage states and earthquake sources on the life-cycle cost and seismic resilience were assessed for retrofitting a deficient bridge bent in this research. Performance-based seismic loss and seismic resilience assessments of as-built bent and bents retrofitted with different retrofit options were executed for life-cycle performance comparison and optimum retrofitting technique selection. ECC jacketed bent had the least crushing probability in most situations. CFRP and steel jacketed bents were subjected to the smallest and highest seismic losses, respectively. ECC jacket was selected as the optimum option for retrofitting the deficient bent because it produced the greatest benefit-cost ratio under most conditions over the other techniques. All retrofitted bents exhibited the highest and lowest seismic resilience under interface and intra-slab earthquakes, respectively. Each retrofitted bent showed the minimum seismic resilience when the yielded rebar proportion mostly increased by 40% for intra-slab earthquakes. CFRP jacket became the optimum technique for retrofitting the deficient bent with maximum seismic resilience and the shortest full-functionality restoration duration.