Optimal Risk-Based Maintenance Planning of Ship Hull Structure

Abstract

Various structures such as marine structures age over time. In order to always maintain safety conditions, maintenance processes including inspection and repair should be implemented on them. Corrosion and fatigue cracks are two main factors that reduce the ultimate strength of the ship’s hull girder over time and thus increase the probability and risk of failure. At the time of inspection, the structural conditions must be checked so that, if necessary, the required repairs can be done on it. The main objective of this paper is to provide optimized maintenance plans of the ship structure based on probabilistic concepts with regard to corrosion and fatigue cracks. Maintenance activities increase the operational costs of ships; therefore, it is advisable to inspect and repair in the optimal times. Optimal maintenance planning of the ship structure can be conducted by formulating and solving a multi-objective optimization problem. The use of risk as a structural performance indicator has become more common in recent years. The objective functions of the optimization problem include minimizing the structure’s lifecycle maintenance costs, including inspection and repair costs, and also minimizing the maximum risk of structural failure during the ship’s life. In the following, to achieve better responses, reliability index has been added to the problem as the third objective function. The multi-objective optimization problem is solved using genetic algorithms. The proposed risk-based approach is applied to the hull structure of a tanker ship.

Keywords

Ship hull girder / Optimum maintenance planning / Lifecycle cost / Risk / Failure consequence / Inspection / Repair / Corrosion / Fatigue cracks

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