Fuzzy Reliability Assessment for Offshore Structures Considering Inspection and Maintenance

It has been shown that probabilistic model is an effective tool in assessing structural reliability incorporating the information from non-destructive inspection (NDT) of offshore structures. However, the preceding theorems fail to adequately deal with the uncertainties of fuzzy character that are associated with NDT for offshore structures. This paper is aimed at an initial investigation on reliability theory of structure involved with fuzziness considering inspection and maintenance. Based on the basic principles of fuzzy set theory, a fuzzy Bayesian procedure is proposed to quantify the fuzzy uncertainty, including the NDT uncertainty in the flaw size determination and the flaw detection, the modeling uncertainty in model selection and the uncertainty in distribution parameter. This paper presents an algorithm to compute the posterior probability of model weights and the posterior distribution of distribution parameter employing the fuzzy Bayesian theorem. The prior probabilities of model weights may be determined based on fuzzy synthetic evaluation. A method for reliability assessment upon inspection and maintenance considering fuzzy uncertainties is put forward in this paper. The example is investigated to illustrate the validation of the proposed method. It is found that the effect of fuzzy uncertainties could be very significant in assessing structural reliability.