Classification of welding-induced residual stresses in gusset joints

Residual stresses generated during welding are well-recognised as a critical factor in structural integrity and design. Advances in computational modelling have enabled increasingly accurate characterisation of residual stress fields, facilitating their integration into modern structural assessments. This study aims to improve the interpretation of welding-induced residual stresses by decomposing them into primary, secondary and tertiary components, and by examining their evolution under varying mechanical boundary conditions and geometrical configurations. To achieve this, a fully coupled thermo-mechanical finite element welding simulation with a validated heat source was employed to model the welding process and quantify residual stresses near a longitudinally welded-around gusset fabricated from quenched-and-tempered 690 high-strength steel. The residual stress state was evaluated both as a total resultant at the weld toe, and through its decomposition into primary and secondary membrane and bending components, together with tertiary nonlinear components. The residual stress components were analysed across the plate width and thickness under varying boundary conditions. A parametric study considered three plate widths and five support configurations at two support distances. The results show that variation in the total residual stress after welding is relatively limited and mainly determined by the support distance, support condition, and support release. In contrast, the magnitudes and distributions of the individual stress components exhibit significantly greater variation, providing insight into the mechanisms underlying the total residual stress state. The findings highlight the importance of joint geometry and welding boundary conditions when assessing welding-induced residual stresses and their influence on the load-carrying capacity of welded structures.