Response of a ship structural detail under low cycle fatigue loading

Most ship structures consist of plate details, connected to longitudinal and transverse members by welded joints, which are the sites of high stress concentrations, and are subject to severe environmental loading from wave pressure, ship motions and loading/unloading operations, which induce significant fatigue loads. The presence of stress concentrations and fatigue loads leads to cyclic stress that exceeds the yield stress locally and some cracks, related to low cycle fatigue (LCF), can be detected in ship structures. From an engineering point of view, the fatigue data obtained by means of tests are useful only if these values can be extended from the small specimens, generally used in the laboratory tests, to real structural details subjected to complex loading conditions. The aim of this research was the strength assessment of a ship welded detail under LCF loading. An experimental set-up was planned and realized for the full-scale fatigue tests of intersections of T-shaped web frames. Moreover extensive finite element analyses of the investigated detail were performed for the analysis of stress pattern at the sites of high stress concentrations.