Multi-criteria robust optimization for bridge adaptation strategies targeting superstructure unseating under coastal natural hazards

The life-cycle management of low-lying coastal bridges exposed to coastal natural hazards (e.g., Hurricane Ivan, Katrina, and the recent Ian) has become an ongoing concern due to the detrimental impacts of these extreme events. The uncertain occurrence of multiple climate drivers and their accompanying influence on the frequency and intensity of coastal hazards further complicates the determination of bridge adaptations. Reliable modeling of the failure probability and consideration for the deep uncertainties associated with climate change are essential to determining retrofit action and implementation time. This study proposes a multi-criteria optimization framework for robust adaptation strategies of coastal bridges. The proposed framework can devise bespoke adaptation strategies towards the dominant superstructure unseating failure, which is enabled by: (a) pragmatic bridge vulnerability analysis rooted in the coupled fluid–structure dynamic numerical analysis; (b) multi-criteria optimization assessing the efficiency and priority of different adaptations; and (c) strategy robustness against the unknown occurrence of imminent climate futures. The exogenous uncertainties associated with future economics and climate scenarios are addressed via sensitivity analysis. To the best knowledge of the authors, this is the first time that robust adaptation strategies are developed for coastal bridges targeting hurricane-induced superstructure damages. These results not only measure the feasibility of various adaptation actions from both economic and engineering aspects but also provide a reference basis for decision-makers.