Probabilistic Seismic Resilience-Based Cost–Benefit Analysis for Bridge Retrofit Assessment

This paper explores a probabilistic resilience-based cost–benefit model that can be used to identify the best retrofit measures for bridges. In the model, the increase in resilience is considered to be the benefit of seismic retrofit. A bridge functionality assessment model is also proposed to evaluate resilience. The functionality is estimated based on the appropriate seismic loss and exponential recovery function models. Then, the functionality assessment model is validated with the field data of the post-earthquake recovery process of bridges. The whole proposed methodology is applied to a non-seismically designed multi-span simply supported concrete girder bridge located in Charleston. Seven retrofit measures, including steel jackets, seat extenders and elastomeric isolation bearings, are applied to the as-built bridge in order to assess their cost-effectiveness. The results show that the cost-effectiveness of retrofit measures varies with the ground motion intensity, and the best retrofit is seat extenders followed by elastomeric isolation bearings when considering the seismic hazard of Charleston. Sensitivity analysis is also performed to identify major uncertain parameters to which the resilience-based cost–benefit ratios are most sensitive. Statistical analysis of resilience-based cost–benefit ratios obtained through random sampling of major uncertain parameters reveals that normal distribution can be used to describe their uncertain nature. The 90% confidence intervals of resilience-based cost–benefit ratios estimated from random sampling also indicate the high cost-effectiveness of seat extenders and elastomeric isolation bearings to enhance bridge performance.