The assessment of the fatigue strength by means of local approaches is very conservative compared with experiments of complex plated structures connected by welded joints. Here, relatively long crack propagation phases were observed. At first, this paper deals with numerical crack propagation simulations which were performed for different geometrical variants. The analyses aim to identify why the life extends if the number of intersected plates increases. In conclusion, the stress gradient over the plate thickness, the apparent plate thickness and the load-carrying grade of the weld slows down the crack propagation rate. Secondly, a correction method is proposed how these effects can be considered in the structural hot-spot stress or effective notch stress approaches. Different reduction factors are introduced which were derived from crack propagation analyses. The factors reduce the local reference stress of the applied approach. Finally, the method is applied to an example of a complex structure, and the computed fatigue strength is compared with test results.
