Probabilistic Fatigue Crack Growth Analysis of Offshore Structures, with Reliability Updating Through Inspection

A stochastic mtiel for fatiguecrackgrowth is applied.which accountsfor uncertainties in loading, initialand critical defectsizes,materialparameters includingspatialvariation,and in the uncertainty relatedto computationof the stressintensityfactor. Failu~ probabilities are computed by first-and second-orderreliability methods and sensitivity factorsare &termined. Model updating based on inserviceinspectionresultsis formulated witfdn the firstkrdereliability method. Updated failureprobabilities arecomputed and thedistributions ofthebasic variables areupdated.Two typesof h-serviceinspectionresultsare used to update the computed failure probabilities. Inspections which do not detect a crack are used and the inspection uncertainty k included in terms of the distribution of nondetwted crack sizes by the specific tnspectlon methcd. inspections which detect a crack are also included and the inspection uncertainty l.s Included through the uncertainty m the measured crack size. The formulation are presented for u@ating based on one or more fnspectioms. A similar formulation for reliability updating after repair 1sprovided within the same framework.