Fatigue assessment of joints at bulb profiles by local approaches

This paper summarizes the research work carried out in Germany and in Italy about the fatigue strength of joints between bulb plate profiles, typically applied by the shipbuilding industry. Fatigue tests of different joint configurations were carried out and several local approaches were applied. The paper focuses on the fatigue assessment approaches based on the notch stress intensity factor, which assume that fatigue is governed by the singular stress field at notch tips. Two approaches, referring to either the local strain energy density or to the peak stress value, are presented and applied. Additionally, a sensitivity investigation regarding the geometry of the weld seam of butt joints was performed on the basis of strain energy density approach. Comparisons with test data and with assessments of other common approaches offer a critical review about where the pros and the limitations of each approach are.