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A cost-benefit model of risk based optimal inspection and repair planning was proposed for the ship structures subjected to corrosion deterioration. The planning problem was formulated as an optimization problem where the total benefit-cost ratio in the expected lifetime was maximized with a constraint on the minimum acceptable reliability index. Based on them, a component was investigated to illustrate the process of the cost-benefit assessment for selecting the optimal inspection and repair strategy. Some sensitivity studies were provided. The results show that the proposed method of risk based cost-benefit analysis can effectively integrate the economy with reliability of the inspection and repair planning. A balance can be achieved between the risk cost and total expected inspection and repair costs by using the proposed method, which is very effective in selecting the optimal inspection and repair strategy. [ABSTRACT FROM AUTHOR]

An optimization model of risk based optimal inspection and repair planning was proposed for the ship structures subjected to corrosion deterioration. The planning problem was formulated as an optimization problem where the expected life costs were minimized with a constraint on the minimum acceptable reliability index. The safety margins were established for the inspection events, the repair events and the failure events for ship structures. Based on them, a component subjected to pitting corrosion was investigated to illustrate the process of selecting the optimal inspection and repair strategy. The results show that the optimal inspection instants should take place before the reliability index reaches the minimum accept able reliability index. A balance can be achieved between the risk cost and total expected inspection and repair costs by using the risk based optimal inspection and repair method, which is very effective in selecting the optimal inspection and repair strategy. [ABSTRACT FROM AUTHOR]

A theoretical framework of risk-based inspection and repair was proposed for the ship structures subjected to corrosion deterioration. A repair index was presented to consider the reliability updating after repair. The reliability updating was performed using the Bayesian updating method. A decision tree was established for selecting the optimal inspection and repair strategy. By comparing the expected costs associated with different inspection and repair strategies, the smallest expected cost associated with the inspection and repair strategy can be identified as the optimal one. Based on them, a method was proposed to perform the sensitivity analysis. Some formulae were derived to analyze the sensitivities. A numerical example was investigated to illustrate the process of selecting the optimal inspection and repair strategy. The results show that the decision tree method is very effective in selecting the optimal inspection and repair strategy. Different values of various costs have significant effects on the reliability and stability of decision results. [ABSTRACT FROM AUTHOR]

Based on the comparison of several existing probability of detection (PoD) models, a new probability of detection model was proposed for the updating of crack size distribution. The theoretical derivation shows that most of the existing PoD models are special cases of the new probability of detection model. The least square method was adopted for determining the values of parameters in PoD models. The new model was also compared with other existing PoD models. The results indicate that the new PoD model can better fit the inspection data. This new PoD model was then applied to analyze the problem of crack size updating for ship structures. The Bayesian updating method was used to analyze the effect of PoD models on the posterior distribution of a crack size. The results show that the different PoD models have a significant effect on the posterior distribution. [ABSTRACT FROM AUTHOR]

The classical probability theory cannot effectively quantify the parameter uncertainty in probability of detection. And the conventional data analytic method and expert judgment method fail to handle the problem of model uncertainty updating with the information from nondestructive inspection. To overcome these disadvantages, a Bayesian approach was proposed. The formulae of multiplication factors to measure the statistical uncertainties in the probability of detection following the Weibull distribution were derived. A Bayesian updating method was applied to compute the posterior probabilities of model weights and the posterior probability density functions of the distribution parameters of probalility of detection. The total probability model method was proposed to analyze the problem of multi-layered model uncertainty updating. This method was then applied to the problem of multi-layered corrosion model uncertainty updating for ship structures. The results indicate that the proposed method is effective. [ABSTRACT FROM AUTHOR]