Risk-informed life-cycle optimum inspection and maintenance of ship structures considering corrosion and fatigue

• Time-variant risk associated with ship flexural failure is computed.
• Effects of corrosion and fatigue crack are considered.
• Risk-informed life-cycle optimum maintenance of ships is provided.
• Genetic algorithm is adopted to solve bi-objective optimization problem.

During its life-cycle, a ship structure may suffer from structural deterioration associated with corrosion and/or fatigue. A prolonged exposure to these hazards results in a reduction of structural resistance which can lead to failure. Optimum inspection and maintenance planning of ship structures is a challenging process needed to ensure ship safety during the life-cycle. This paper presents a probabilistic approach to provide optimum inspection and repair plans for ship structures considering corrosion and fatigue. Uncertainties in the damage assessment associated with corrosion and fatigue are taken into account. Risk is assessed by considering the direct losses associated with flexural failure. A multi-objective optimization problem, which accounts for structural deterioration scenarios and various uncertainties, is formulated to find the optimum inspection and repair planning of ship structures. The life-cycle risk associated with flexural failure and expected total inspection and maintenance costs are considered as conflicting criteria. The proposed probabilistic optimization approach is illustrated on the VLCC ship structure. Genetic algorithms are used to solve the optimization problem.