Stability analysis of multi-story steel frames subjected to different axial load

Abstract

This paper presents a stability analysis of multi-story steel frames in the elastic and elasto-plastic domain. The concept of the tangent modulus theory is applied. Numerical analysis is carried out using FEM where corresponding stiffness matrices are based upon the trigonometric and hyperbolic interpolation functions of normal forces. Also, the calculation algorithm is based on the global stability analysis of the considered frames. The numerical analysis is performed using the self-developed computer program ALIN. A six-story three-bay steel frame was chosen as a benchmark numerical example. Sway and non-sway frames that are clamped at the base are analyzed separately. Two load cases are considered: when the axial forces are applied at the top of the frame and when these forces are applied at each story of the frame. From the obtained results it is obvious the weakness of the traditional elastic stability analysis. Therefore, stability analysis in the inelastic domain is recommended, especially in the case of rigid structures.