Strength of biaxially loaded slender I-section beam-columns

Abstract

The strength of a slender section is governed by local buckling of its elements. The local buckling mode is mainly affected by the width to thickness ratios of elements forming the section and the member slenderness ratio. A nonlinear finite element model was developed in this paper to study the effect of the mentioned factors on the capacity of biaxially loaded slender I-section beam–columns. A group of I sections was selected with varying flange width to flange thickness and web width to web thickness ratios. Different member slenderness ratios were chosen to study the different modes of failure. The results show that the linear interaction equation is safe and provides a good fit to the ultimate capacity of members with intermediate slenderness ratios. It is conservative, however, for short member slenderness ratios. Lastly, compared with the newly developed finite element model, the 1996 edition of the American Iron and Steel Institute specification for cold-formed steel structural members and the European Committee for Standardization Eurocode 3 conservatively predict the capacity of members, especially for large ratios of minor axis to major axis bending.Key words: structural engineering, steel, stability, buckling, biaxial loads, ultimate strength.