Effect of Residual Stresses on the Column Flexural Buckling Curves

Hot rolled structural steel shapes develop residual stresses due to non-uniform cooling after hot-rolling. Depending on the geometry, and size of the shapes, the magnitude and distribution of these residual stresses can vary significantly in members which can substantially affect their structural performances. Hence, it is essential to accurately predict the magnitude and distribution of residual stresses in steel structural members. This paper presents an experimentally validated computational technique to simulate multiaxial residual stresses in structural steel W shapes by using a thermo-mechanical analysis. The numerical scheme developed is used to investigate the effect of residual stresses on the flexural buckling strength of columns having different slenderness ratio, depth-to-width ratio and flange thickness. The results of the study demonstrate that the presence of residual stress decreases the flexural buckling strength of rolled W shape steel columns mostly in the inelastic buckling range and the effect varies with the depth-to-width ratio and flange thickness of the members. For heavy W shapes, the effect of residual stress is more prominent than non-heavy W shapes due to the presence of larger compressive residual stresses on the flange. Further analyses are performed to develop column flexural buckling curves for several W shapes having different depth-to-width ratio and flange thicknesses by considering the multiaxial residual stresses and compared against the AISC 360 column design curve to understand the applicability of the AISC 360 column design curve for heavy W shapes, and whether any improvement is necessary.