Definition of Hot Spot Stress in Welded Structure for Fatigue Assessment (3rd Report)

Abstract

In designing a large marine structures, assessment of fatigue strength is one of major design considerations. In the evaluation of fatigue strength of weld toes, it is important to analyze fatigue strength data of structural model in terms of “hot spot stress” due to structural discontinuity, in a simple way but as accurate as possible.In the first report, the authors defined the “hot spot stress” based on fatigue tests for plate type structural components by linear extrapolation of measured strain at two specified points differently distant from welded toe. In the second report, use of peak strain instead of hot spot stress was attempted to seek the practical method.In this report, the authors have attempted to evaluate the applicability of simplified finite element analysis to estimate hot spot stress on the basis of its practicality. For five structural models, several different computations were made to compare each other in order to obtain an acceptable and appropriate modelling method using shell element. The proposed method gives about 10 % conservative estimate of stress for fatigue assessment.