ABSTRACT
The recent occurrence of large scale hurricanes in the south and northeast regions of the United States and their subsequent damage to the infrastructure has highlighted the importance of considering hurricanes in the design and management of coastal bridges. These bridges have the propensity to fail due to deck unseating; typically, the weight of the superstructure is the only resisting mechanism to uplift forces. Additionally, coastal bridges exist in corrosive environments and the resulting deterioration adversely affects the performance of the bridge under both hurricanes and traffic.
Repair and retrofit measures can significantly improve the life-cycle performance. Moreover, optimal management plans can be developed to mitigate life-cycle risk. However, the management of coastal bridges must incorporate all prevalent and predominant hazards.
This paper incorporates two major hazards, hurricanes and traffic, in a risk-based optimal management routine to exemplify the impact of location on risk mitigation strategies for deteriorating bridges in coastal regions. It implements bi-objective optimization in order to determine the optimal timing and types of repair and retrofit actions while simultaneously minimizing the maximum life-cycle risk and maintenance/retrofit costs. The inclusion of the maximum life-cycle risk indicator allows for the consideration of the uncertainties in the hazard and structural response, as well as the economic, environmental, and social consequences of bridge failure.
The two conflicting objectives in the proposed optimization problem yield a Pareto-optimal set of solutions which elucidate the tradeoff between the objectives. That is, in order to reduce the maximum life-cycle risk, a higher maintenance cost is needed. This paper also investigates the effect of bridge location on the optimal management strategies of coastal bridges. A comparative study is performed to highlight the cost-benefit ratio of adding restrainers, as a retrofit measure, in regions with different exposure to hurricanes. The proposed approach is applied to simply support steel bridges located in both coastal regions of New York and Florida.
