Fatigue reliability assessment of a complex welded structure subjected to multiple cracks

A probabilistic approach for fatigue reliability assessment of a complicated ship welded structure subjected to a correlated growth of multiple site cracks is developed here. It is assumed that five through thickness cracks will initiate and propagate at the critical hotspots in the web frame structure. Stress intensity factors at the tips of cracks, considering all possible combinations of all cracks of different lengths, are calculated by finite element analysis. The geometry correction functions of the five cracks, as a function of a crack size are determined by using nonlinear regression analysis estimating the statistical descriptors of the five geometry correction functions. The Paris-Erdogan law is used to predict the fatigue crack propagation life. Fatigue reliability of the web-frame welded structure is evaluated while accounting for the correlation between any two-fatigue failure modes caused by multiple site fatigue cracks propagating in the welded structure.