Fatigue strength assessment of scallops —an example for the application of nominal and local stress approaches

Abstract

Scallops, i.e. small cut-outs in ship structural members, are frequently subjected to high cyclic stresses, which require fatigue strength to be considered during structural design. The paper summarizes the results of several fatigue tests for various types of scallops under axial loading. Further types and the effect of complex load combinations are evaluated using local approaches for the fatigue strength assessment, in particular the notch stress approach for plate edges and the structural or hot-spot stress approach for welded connections. After a review of the approaches, the analysis of local stresses by the finite element method and by stress concentration factors (SCFs) is described. Regression formulae for SCFs, derived from parametric stress analyses, are presented for elliptical and rectangular scallops with rounded corners. The approaches are illustrated by examples from which conclusions for the practical application are drawn.