Limit state capacities for global performance assessment of bridges exposed to hurricane surge and wave

Past failure of coastal bridges during hurricanes has revealed the vulnerability of these structures to wave and storm surge loading, thus signifying the need for reliability assessment of coastal bridges to provide a basis for hurricane risk assessment and mitigation. Such a reliability assessment requires probabilistic estimation of the capacity and demand of the structure, which are often conveniently decoupled to support risk assessment of existing bridges as well as performance based design or retrofit. This paper presents a new approach for probabilistic analysis of limit state capacities for bridge systems, in which local response quantities from numerical simulations are mapped to global performance measures, such as system strength and stiffness loss. Four different configurations of a case study bridge are analyzed to derive probabilistic models of the limit state capacities, revealing the significant bridge component demand parameters that contribute to the global (system) damage levels and the mathematical form of the limit state capacities, along with uncertainty quantification. Such models can be used in reliability assessment of coastal bridges and extended to evaluate the effectiveness of alternative retrofit measures proposed for unseating prevention. The proposed approach for global performance assessment complements emerging interests in multi-hazard analysis and system reliability of bridges by providing a new perspective on identifying the joint local damages which affect global behaviors that relate to practical decision making on post-event bridge functionality.