Marine Component Fatigue Reliability

Abstract

A method is presented for evaluating the fatigue of offshore structural steel members based on structural component reliability procedures coupled with spectral analysis methods. The approach is based on formulating a nonlinear performance function that expresses the cumulative fatigure damage in the form of Miner's rule. Uncertainties in the cumulative fatigue damage rule and stress calculation are handled by the treatment of the parameters in question as random variables. As a measure of reliability against fatigue, the Hasofer‐Lind reliability index of the performance function is calculated using the first‐order marginal distribution method. The approach is invariant, accounts for correlation among random variables, and permits the ordering of the random variables and deterministic parameters to be readily performed. A numerical application on a simple idealized platform is used to demonstrate the method and study the fatigue reliability sensitivity. Results of the analysis indicate that the reliability is most sensitive to uncertainty in the stress calculation.