Fatigue Crack Initiation and Propagation at a Bracket End Weld Toe

Abstract

Tank corner members of semi-membrane or prismatic independent tanks are one of the most important structural members of LPG carriers. As most tank corner members are furnished with brackets, fatigue crack initiation at a bracket end weld toe and propagation along the bead toe are throughly investigated in the paper. Two types of loading patterns were employed in fatigue tests ; 1) Constant amplitude loading and 2) random loading which simulated actual load exerted upon the tanks of LPG carriers. It was confirmed through the experiment that fatigue crack initiated at a bracket end weld toe and propagated along the bead toe. In the paper, the authers presented a method of analysing the fatigue strength of the weld joint between tank corner member and the bracket. In the analysis, stress categories were classified and the effect of structural discontinuity due to the bracket and stress concentration due to weld bead were fully taken into account.