Influence of welding distortion on the structural stress in thin deck panels

This paper investigates the effect of welding distortions on the structural stress used in fatigue assessment of thin stiffened panels with the plate thickness of 3-4 mm. Comprehensive geometry measurements are carried out for full-scale thin deck structures. The influence of shape and magnitude of initial distortion is studied using geometrically nonlinear finite element analysis. The results are validated with the strains measured prior fatigue testing of full-scale thin deck panel and very good agreement is observed. The results reveal that the shape of the welding distortion is influencing the structural stresses more than the magnitude. At the same time, the magnitude dictates the location of maximum stress along the transverse butt weld. In addition, it is found surprisingly that for relatively small initial distortion, the geometrical nonlinearity, i.e. straightening, is more significant than in largely distorted panel. This is due to the fact that both initially flat and significantly distorted panels have relatively strictlydefined shapes which behave almost linearly. In case of intermediate distortions, the structure needs to find equilibrium from several possible shapes, highlighting the non-linearity. The conclusion of the work is that simplified modeling of thin panel initial shape can cause significant error in fatigue assessment.