船体结构腐蚀模型对检测及维修规划的影响

Effect of Corrosion Model on Inspection and Repair Planning for Ship Structures

提出了基于风险的船体结构腐蚀优化检测及维修的基本理论框架。最优的检测及维修 ,是在保证结构在设计工作寿命内的可靠指标大于最低可靠指标的基础上 ,使结构生命周期内总的期望费用最小。建立了检测、维修及失效事件的安全余量方程 ,推导了失效及维修概率的计算公式。在此基础上 ,以船体结构两种常用的腐蚀模型 Paik模型和 Guedes Soares模型为例 ,分析了两种模型对最优检测及维修策略的影响。其结果表明 ,腐蚀模型对最优的检测及维修次数和时间有明显的影响 ,但是对总的期望费用及失效概率影响不大 ,而且两种腐蚀模型得出的最优失效概率都是 1 0 - 3。

In order to ensure the safety and reliability of ship structures during thei r service lifetime, inspections are essential to evaluating corrosion and fatigu e damage and scheduling maintenance or repair. Generally, the traditional inspec tion planning may not only incur higher costs but also result in unnecessary ins pections. Therefore, it is necessary to investigate the optimal inspection and r epair planning to accomplish the most cost-effective inspection and to achieve a balance between the risk costs and the inspection and repair costs. At the sa me time, there are several empirical corrosion models to describe typical corr osion behavior in ship structures. Moreover, there is no literature to demonstra te which model is better, so it is difficult for us to decide which model should be used to select the optimal inspection and repair planning. In this situation , the uncertainty from the selection of the corrosion deterioration model arises in developing the optimal inspection and repair planning. To solve the foregoing problems, a theoretical framework of risk based optimal i nsp ection and repair planning is proposed for the ship structures subjected to corr osion deterioration. The planning problem is formulated as an optimization prob lem where the expected lifetime costs are minimized with a constraint on the mi nimum acceptable reliability index. The safety margins are established for the i nspection events, the repair events and the failure events of ship structures, a nd the formulae used for calculating failure probabilities and repair probabilit ies are derived. Based on them, two corrosion models, namely Paik's model and G uedes Soares' model, are adopted for analyzing the effect of model uncertainty o n the optimal inspection and repair planning for ship structures. The results sh ow that the corrosion model uncertainty has a significant influence on the optim al number of inspection and repair, time of inspection and repair, but has insig nificant influence on the total expected costs and total probability of failure. The optimal target failure probability is 10 -3 for both corrosion models.