A Structural Design Approach for Controlling Welding Distortion at the Upper Deck of a Hull Structure in the Erection Stage

An effective design method for controlling the transitional welding distortion at the aft upper deck occurring in the erection stage of the hull structure has been established using FEA and measured distortion database. Variation of distortion at the aft upper deck was measured according to the progress of the manufacturing process. This was done in order to clarify the 2 nd distortion of the upper deck, defined as the increment of welding distortion developed after the assembly stage, The amount and distribution of the 2 nd load causing the 2 nd distortion were identified with a non-linear buckling FEA. The distribution of the welding distortion and the residual stress were assumed to be initial imperfections, which were identified with STEM (simplified thermoelastic method) based on inherent strain. Based on these results, the modification of structural design parameters such as plate thickness and the attachment of carling were made, in order to prevent the excessive 2 nd distortion which requires costly flame correction work in the erection stage.