Time-dependent Reliability Assessment of Mooring Systems

摘要

Floating production facilities are widely used in the exploitation ofrnoffshore oil and gas. Mooring system is the key structure componentrnanchoring the floating system to sea bed. The structural reliabilityrnapproach may be used for the structural analysis and design taking tornaccount uncertainties related to both applied loading and materialrnstrength and time dependent degradation mechanisms. By thernconsideration of corrosion as the main cause of resistance deterioration,rna time-dependent reliability analysis method can be used to investigaternthe ultimate strength of mooring system under wind, wave and currentrnconditions that is presented in this paper. The paper also reviews a casernstudy of the mooring system of “Huajiachi” test facility that a reliabilityrnmodel was developed to analyze the probability of declining resistancernwith time. The probability distribution function of the total loads wasrncreated by Matlab software using the metocean data. The comparisonrnbetween time-dependent and time-invariant reliability assessmentrnmethods shows that the analysis results without considering timernvariation are lack of security. During design life, it’s necessary tornregularly assess integrity of mooring system and if any deficiency orrnrisk is identified, a mooring line replacement program should berndeveloped. Finally, based on the formulated model, the mooring systemrnreliability analysis is subsequently performed which can provide arnbetter understanding of potential risks.