Sensitivity analysis on fatigue reliability and inspection of ship structural members

Abstract

Sensitivity analysis on fatigue reliability and inspection is carried out for a typical structural member of bulk carrier. Fatigue properties of the member and probability of crack detection at the field inspection are obtained by the questionnaire asked to the naval engineers. Changing stress level (fatigue life) of the member, crack growth curve and inspection interval as parameters around a standard condition, failure probabilities of member during 20 years' service are calculated by the Markov chain model. The result of analysis can suggest the solutions for design requirements such as improvement of reliability level, reduction of structural weight and the simplification of inspection. In the latter part of the paper, effectiveness of combined inspection method and sampling inspection method are discussed through the sensitivity analysis assuming member sets having different number of initiated cracks. It is found that combined inspection has more advantage than sampling inspection, when the number of members having initiated crack is a few in the inspecting member set.