Development of Performance-Based Fragility Curves of Coastal Bridges Subjected to Extreme Wave-Induced Loads

A number of coastal bridges faced significant damage due to recent natural hazards, inducing extreme waves. The fragility function is the basic step for assessing the resilience of a structure, thereby allowing the designers to alleviate post-event structural disasters and develop improved design methods for new structures. The majority of the focus of fragility functions developed in literature are concentrated on superstructure components and wave load on bridge decks. This paper presents a simplified methodology for the definition of damage states of the substructure component (pier drift) due to wave loads acting on piers as well as the bridge deck. The hazard intensity parameters representing the extreme wave loads chosen for this study are wave period, wave height, and still water depth. The Latin hypercube sampling technique is applied to consider the uncertainties in the intensity parameters as well as the material properties for the finite-element bridge models. Results indicate that the wave period is the most dominant factor affecting the wave-load intensity. The deck-level loading caused a higher probability of failure compared with the pier-level wave loading scenario. In both loading scenarios considered, the elastomeric bearing and shear keys are found to be one of the most vulnerable components in the system-level fragility curves developed. The system-fragility curves generated in this paper can be used to assess the resiliency of coastal bridges subjected to extreme wave-induced loads. The findings of this paper will also add to the risk mitigation and reliability assessment of coastal structures under multi-hazard conditions.