The influence of residual stress on the ultimate strength of longitudinally compressed stiffened panels

Welding-induced residual stress is known to reduce the ultimate compressive strength of moderately slender stiffened panels under longitudinal compression. This paper contributes a quantified measure of this strength reduction and draws some qualitative observations linking the significance of the residual stress influence to the collapse mode of the panel. A series of nonlinear finite element analyses are completed which covers a range of plate slenderness ratios (beta = 1.0 - 4.0) and column slenderness ratios (lambda = 0.2 - 1.2) typical for application to ship structures. Two residual stress scenarios are compared to a baseline stress-free condition. The first scenario includes residual stress in the plate only and the second scenario includes residual stress applied in the plate and the stiffener web. A modified edge function approach, which can be used in combination with a rule-based approach to account for the effects of residual stress, is examined with reference to the numerical results. A significant ultimate strength reduction due to residual stress is found in most test cases. It is found that residual stress in the plate causes a reduction of the ultimate compressive strength of stiffened panels regardless of failure modes. However, the residual stress in the stiffener web dominates the strength reduction of stiffened panels where collapse is triggered by beam-column buckling. Conversely it has little influence on the stiffened panels which collapse in a plate buckling mode. In addition, the modified edge function approach is demonstrated as conservative compared to the present numerical results, with its applicability confined to stocky panels.

Automated summary

This paper investigates the effect of welding-induced residual stress on the strength of stiffened panels and finds that residual stress significantly reduces the ultimate compressive strength of the panels. The study concludes that residual stress in the plate causes a reduction in strength regardless of failure modes, while residual stress in the stiffener web dominates the strength reduction in cases of collapse due to beam-column buckling. The modified edge function approach is shown to be conservative compared to numerical results and is applicable only to stocky panels.