Influence of inspection on the safety of fatigue loaded welded cruciform steel joints – comparison of simplified and advanced crack growth models

Probabilistic fatigue life prediction models of welded steel joints are often used to estimate the level of safety, which is given in terms of the probability of failure or the reliability index as a function of the applied load cycles. Prediction models based on fracture mechanics allow taking into account the effect of inspections on the estimated level of safety. Recent developments in fracture mechanics based fatigue prediction models allow modeling the behavior of short and long fatigue cracks under constant and variable amplitude loading. Short cracks are relevant since their growth characterizes most of the fatigue life, especially under service loading. A recently proposed model by the authors is considered and compared to a more traditional and simplified model as proposed in the standard BS7910, where no distinction is made between short and long cracks. The effect of the model uncertainty, the type of inspection, and the time of the inspection on the estimated level of safety are quantified for welded cruciform steel joints.