Fatigue assessments have been predominantly carried out with quasi-deterministic approaches, such asthe use of S–N curves. However, both the loading and the resistance of fatigue prone components aresubjected to important uncertainties. Consequently, a prediction of the remaining fatigue life based ondeterministic load and resistance models is highly unreliable and a reliability-based approach shouldpreferably be implemented. In order to consider all potential crack growth stages, crack initiation andstable crack propagation have to be accounted for. This paper first presents the strain-based correlationapproach used to predict the initiation life and the linear elastic fracture mechanics approach employed tomodel the propagation life. A brief outline of the randomness in loading and the subsequent response ofindividual components are given. The variability in fatigue material properties of commonly used structuralsteel and matching weld metal is assessed. The results of small scale tests and finite element analysesare used with Monte Carlo simulations to estimate the variability and reliability of fatigue life predictions.
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