English

Abstract

Welded marine structures like ships and offshore structures are susceptible to fatigue cracking. Structural discontinuities lead in general to stress concentrations that significantly affect fatigue strength. The effect of stress concentrations may be accounted by the hot-spot stress approach using linear extrapolation of surface stresses. A longitudinal attachment weld is studied experimentally and by FE analyses. The detailed stress measurements are used to evaluate various modelling techniques in FE analysis. The solid element and the shell element models are studied. The different models for inclusion of weld stiffness are studied, with solid elements and shell elements. Based on the results, recommendations are given for choice of element model and mesh size. The S-N data are generated for the as-welded condition and for the specimens that had been preloaded to levels representing ultimate load conditions for welded structures. The data are compared with current design practices for fatigue strength of welded structures.