Strength of Thin- and Thick-Walled Metal Beam–Columns Bent in Single and Double Curvature

The theoretical behavior of inelastic beam–columns subjected to axial load and biaxial bending is presented in detail, including the simultaneous effects of initial imperfections, residual stresses, and local buckling, particularly in thin-walled cross sections. Prismatic beam–columns with both symmetrical and asymmetrical cross sections under proportional and nonproportional loading conditions can be analyzed. In addition to predicting axial load and moment capacity, the model calculates transverse deflections and rotations along the member, which are then compared with experimental and theoretical results available in the technical literature. These comparisons demonstrate the model’s ability to accurately predict the behavior and strength of beam–columns under biaxial bending, whether bent in single or double curvature. Various loading paths can be studied, including concentric and eccentric axial loads, end moments, and both point and distributed lateral loads. The main objective of this paper is to present a practical tool for the design and analysis of pinned-pinned beam–columns made of steel, aluminum, and other metals. The proposed model takes the computational advantages of ignoring the effects of shear and torsion, and uses small-deflection theory to calculate the resistance of beam–columns under biaxial bending. Comparisons with experimental data from the scientific literature demonstrated that, despite these simplifications, the model yields acceptable predictions for failure loads, transverse deflections, and member rotations.