Nonlinear collapse analysis of stiffened plates considering welding-induced residual stress and distortion

Numerical simulation based on finite element modelling is used to study the influence of residual stress and distortion on the behaviour of tee- and angle-stiffened plates under axial compression. Residual stress and distortion due to welding of the stiffener to the plate are calculated by three-dimensioanl thermo-elasto-plastic finite element analysis. The behaviour of 14 stiffened plates under compressive axial loads is evaluated both with and without welding-induced residual stress and the results are compared with classification society design equations. The results show that the ultimate strength of angle- and tee-stiffened plates may be reduced by as much as 12.5% due to the presence of welding-induced residual stress. Comparison of load-shortening curves generated by finite element analysis with those derived from International Association of Classification Societies (IACS) design equations for both types of stiffener shows that for ultimate strength, the two methods compare well. In the post-ultimate portion of the load-shortening curves, IACS design equations are found to overestimate the post-ultimate capacity of stiffened plates which may affect the accuracy of ultimate strength calculations for ship hull girders.