To ensure the safety and reliability of ship structures during their service lifetime, inspections are essential to evaluate corrosion or fatigue damage and schedule maintenance or repair. This paper aims to propose a cost-benefit model of risk based inspection and repair planning for ship structures subjected to corrosion deterioration. The models of expected costs and expected benefit are formulated. The benefit-cost ratio is adopted to select the optimal inspection and repair planning. The planning problem is formulated as an optimization problem where the total benefit-cost ratio in the expected lifetime is maximized with a constraint on the minimum acceptable reliability index. A component subjected to corrosion deterioration is presented to illustrate the proposed approach. In addition, sensitivity studies are presented to account for the effects of uncertainties in basic parameters on the benefit-cost ratio and the optimal inspection and repair planning. The results indicate that the proposed approach can effectively integrate the economy with reliability of the inspection and repair planning. Furthermore, a balance can be achieved between the risk cost and total expected inspection and repair costs, which is very effective in selecting the optimal inspection and repair planning. Parametric studies show that the benefit-cost ratio is sensitive to the time of inspection and repair, the reference period, the repair criterion and the failure criterion.

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