Bending strength of singly-symmetric overhanging floor I-beams

Abstract

The design of the overhanging singly-symmetric I-beams is not sufficiently covered in the current standards and specifications. The buckling length coefficients specified in the current standards and specifications were firstly defined by Nethercot (1973) [1], and cover only doubly symmetric I-sections.The elastic and inelastic behavior of overhanging singly-symmetric floor beams subjected to concentrated load at cantilever tip is investigated in this paper, using the finite element method. To this purpose, a geometrically and materially non-linear finite element model is built. A parametric study is performed considering the effect of mono-symmetric ratio, the un-supported length to the radius of gyration for lateral-torsional buckling ratio, and different boundary conditions at root support and cantilever tip on the ultimate moment capacity of the overhanging beams. Beams with different mono-symmetric ratios are analyzed and the effect of vertical stiffener at root support is considered in this study. It is found that the different boundary conditions and cantilever length have significant effect on the ultimate moment capacity of such beams.Based on the analysis results, handy design models for the ultimate moment capacity of overhanging singly-symmetric floor beams are developed and presented herein. The numerical results have been compared to the simple models presented in AISC (2010), Specification [2] and BS 5950-1:2000 [3].