Fragility Analysis of Retrofitted Multicolumn Bridge Bent Subjected to Near-Fault and Far-Field Ground Motion

This paper focuses on the fragility-based seismic vulnerability assessment of retrofitted multicolumn bridge bents. Fragility curves are developed to assess the relative performance of various retrofit methods under both near-fault and far-field ground motions. A probabilistic seismic demand model (PSDM) is used in generating the fragility functions. Through nonlinear dynamic analysis, fragility curves are developed for multicolumn bridge bents retrofitted with four different retrofit techniques, specifically carbon fiber–reinforced polymer (CFRP) jacketing, steel jacketing, concrete jacketing, and engineered cementitious composite (ECC) jacketing. Following the performance-based evaluation approach, this study aims to investigate the effectiveness of different retrofitting methods to minimize the overall seismic vulnerability of deficient bridge bents. To investigate the seismic responses of the retrofitted bridge bents, a total of 40 earthquake excitations, of which 20 are near-fault and 20 are far-field ground motions, are utilized to evaluate the likelihood of exceeding the seismic capacity of the retrofitted bridge bents. The use of fragility curves for retrofitted bridge bents will aid in expressing the potential impact of retrofit on the bridge bent vulnerability. The results obtained from this study indicate that the bridge bents retrofitted with ECC and CFRP jacketing possess less vulnerability at different damage states under both near-fault and far-field earthquakes.