Incorporation of risk and updating in inspection of fatigue-sensitive details of ship structures

Fatigue cracks, as a structural deterioration mechanism, may lead to unanticipated out of service of naval ships. Consequently, risk assessment and effective inspection planning of naval ships under fatigue damage are needed to achieve economic and sustainable performance of these structures. This paper presents a probabilistic framework for fatigue risk and updating assessment and updating through inspection events. The computation associated with fatigue damage is performed using fracture mechanics and uncertainties are considered within this process. Furthermore, a quantitative risk assessment model using rating functions is presented to identify inspection priority among multiple fatigue-sensitive details. Bayesian techniques are adopted for reliability and risk updating of both inspected and uninspected fatigue-sensitive details at component and system levels. Additionally, correlation of fatigue damage among different critical details is considered and incorporated within risk assessment and updating. A number of analyses are performed to investigate the fatigue risk ranking assessment and updating. Applications are presented on an existing tanker with multiple fatigue-sensitive details.