SEISMIC RETROFIT OF SUBSTANDARD RC BRIDGES USING CONTEMPORARY MITIGATION MEASURES

As essential infrastructure components, existing substandard bridges may cause significant economic losses at the urban scale as they are prone to different damage modes under seismic excitations. Due to the large number of existing RC bridges in earthquake-prone regions and the continuous updates in seismic design criteria, there is increasing interest in developing effective seismic retrofit techniques for enhancing the performance of these structures. This study thus investigates the effectiveness of contemporary retrofit measures for upgrading the seismic performance of RC bridges, namely ultra-high-performance concrete (UHPC) jackets and self-centering energy dissipating (SCED) braces. Detailed fiber-based numerical models are developed for scaled RC bridge substructures retrofitted with the adopted mitigation measures. The hysteretic behavior of the bridge substructures from quasi-static cyclic loading experiments conducted in previous studies is utilized to verify the developed fiberbased models. The validated modeling approaches of retrofit strategies are then applied to an old benchmark bridge located in a medium seismicity zone. The inelastic response of the benchmark bridge substructure before and after the retrofit with different mitigation measures is assessed using the verified fiber-based numerical models. The results demonstrate that the retrofit measures increased the lateral strength of the bridge bent by 37.5%. Also, 10% improved ductility was observed in the UHPC retrofitted bent. This performance assessment study enabled the selection of effective measures to mitigate the vulnerability of substandard bridge members to ensure their post-earthquake functionality.