Experimental validation of an analytical stress magnification factor for thin plates with welding-induced curvature

Lightweight thin-walled superstructure decks enhance cruise ship efficiency and payload but require precise modelling and costly fatigue analyses due to welding-induced distortions in butt-welded thin plates. For more efficient fatigue assessment, this paper validates an analytical model for thin and slender butt-welded plates with initial curvatures using a second-order beam theory. Tensile tests on 4-mm thick butt-welded plates were conducted to measure the structural stress magnification factor (𝑘𝑚), the ratio of structural to nominal stress near the weld. 3D scanning was used to characterise the initial distortions for the analytical modelling of the curvature. The curvature is well-represented by a half-sine shape with amplitude equal to the maximum amplitude measured on the distorted plate. The analytical 𝑘𝑚 factor was validated with an 8% accuracy, while neglecting the curvature led to non-conservative estimates with a 25% mean error.