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Bridges exposed to flooding, hurricanes, tsunamis, and other extreme hydrologic events have been observed to fail due to deck dislodgement, pier failure, or foundation failure. However, the risk assessment and retrofit methodologies for these bridges have typically only been developed around a single failure mode. This paper addresses this gap by integrating the three observed failure modes for bridges vulnerable to extreme hydraulic events into a comprehensive risk assessment framework. Through the use of an event tree, the methodology accounts for the different consequences of failure associated with different failure modes. Bridge management strategies are investigated to determine the effectiveness of the retrofit actions with respect to their benefit (i.e. reduction in risk) and costs. An illustrative example for riverine bridges under various exposure scenarios is presented. The risk assessment and benefit-cost analysis elucidate the need to incorporate all pertinent failure modes of the structure by highlighting the competing nature of different failure modes. The illustrative example shows that the effective management of structures is site-specific and, that the intensity of the hazard at the bridge location affects which management strategy is preferred. The sensitivity to exposure level indicates that the optimal management of the structure should incorporate considerations for potential future changes in the intensity and frequency of the hazard. [ABSTRACT FROM AUTHOR]

This paper proposes an approach for developing optimal risk-based management strategies for bridges in coastal regions. Currently, bridge management strategies in these regions are designed to limit the negative effects corrosion has on bridge performance under traffic loads. However, recent large-scale hurricanes and their associated damage to bridges have demonstrated the need to consider hurricanes when making bridge management decisions. This paper aims to develop optimal risk-based management strategies that include both repair actions to address deteriorating performance under traffic loads and retrofit actions to minimize the potential for failure during hurricanes. The proposed approach considers the uncertainties associated with hazards, and the economic, social, and environmental consequences of failure under traffic loads and hurricanes. The optimal management strategies are achieved by formulating and solving a multiobjective optimization problem. The objectives of this optimization problem include minimizing the lifecycle costs accrued due to repair and retrofit actions and minimizing the maximum risk over the lifecycle of the bridge. The proposed risk-based approach is applied to a steel girder bridge located in a hurricane-prone region. [ABSTRACT FROM AUTHOR]