This final year’s project investigates the interactive buckling behavior of thin-walled rectangular steel section columns subjected to axial compression through a point load. These structural members can be efficient and lightweight but can also be highly sensitive during the interaction of local ang global buckling phenomena. This interaction might result in instability which leads to premature failure and imperfection sensitivity, posing challenges to the current design approaches. Finite element analysis (FEA) has been used by ABAQUS software to precisely simulate the realistic effects of the boundary conditions, material nonlinearity, geometric imperfections and residual stresses. Particular attention was given to the presence of residual stress due to the welding process, since they have shown a significant reduction in structural capacity.