Proposed design model of overhanging C-beams

Abstract

Open cross sections are used in structural applications to resist bending moments. The buckling length specified in the current standards and specifications was firstly defined by Nethercot [13] and covered only doubly symmetric I-sections. In this research, a theoretical program was performed to study the elastic and inelastic behavior of overhanging C-section beams bent about the major axis. A finite element model, correlated well with experimental results, was used in this study to perform a parametric study. Nonlinear geometrical and material analyses were incorporated in the model. Four types of lateral supports at the tip of the overhanging beams were studied. The effect of different boundary conditions at the root (intermediate support) of the overhanging beams was studied. Only concentrated load at the tip was considered. Three different loading positions, with respect to cross-section height, were studied. Based on the parametric study, proposed design model, taking into consideration the effect of different parameters on the ultimate moment capacity of such beams, was presented. Modified effective buckling lengths of such beams were compared to those suggested by SSRC Guide [8], which were incorporated in most current standards and specifications. This comparison showed that the ultimate moment capacities of such beams computed according to AISC Specification [1], BS5950 [3], Eurocode3 [7] and ECP [5] varied from overconservative up to 85% to unconservative up to 15%, depending on the overhanging length, back span length, boundary conditions and the load location along the beam depth.