Resilience-based countermeasure strategy for bridges under multiple hazards

This paper presents a methodology for identifying optimal pre-disaster strategies for bridges subjected to ground motion and tsunami. The seismic and tsunami hazard curves are estimated based on the Monte Carlo simulation considering the uncertainties associated with fault movement. The seismic and tsunami fragility curves of a bridge pier and bearing are developed by numerical methods. The optimization problem for maximizing the benefit-cost ratio and the resilience is solved to identify the bridges necessary to be retrofitted before the event or replaced immediately after the event and find the optimal countermeasures based on the post-disaster road network functionality depending on the damage state of individual bridges. The application to the road network in Wakayama City expected to be affected by the anticipated Nankai Trough earthquake demonstrates that the proposed method can provide the optimal strategies for bridge management to enhance the road network resilience under budget constraints.