Proposed design model for singly-symmetric overhanging monorail I-beams

• Nonlinear finite element model is created to study the behavior of singly-symmetric overhanging monorail I-beams.
• Effect of different boundary conditions at the supports and the tip of such beams is studied.
• Current standards and specifications resulted in unconservative to overconservative design for such beams.
• Handy design model is proposed for the design of singly-symmetric overhanging monorail I-beams.

One special type of overhanging beams is the monorail type. The inability of restraining the bottom flange of the monorail beams leads to poor boundary conditions, especially, at the root support (interior support), which reduces the beam strength. The buckling length coefficients, used in the current standards and specifications, were firstly defined by Nethercot [10], which was conducted for the doubly-symmetric I-sections. The effect of the poor boundary conditions of the monorail beams was not considered by Nethercot [10] and accordingly was not considered by any of the current standards and specifications. In this study, a finite element model, correlated well with the experimental results, was used to investigate the behavior and the strength of singly-symmetric overhanging monorail I-beams. Nonlinear geometrical and material analyses were considered in this research. A parametric study was conducted, using the verified finite element model, to investigate the effect of different boundary conditions, at the root support and the tip, on the ultimate moment capacities of such beams. The study showed that the boundary conditions and the cantilever lengths as well as the mono-symmetric ratio had significant effect on the ultimate moment capacity and the main mode of failure of such beams. Based on the parametric study results, a handy design model was proposed. The study showed that the ultimate moment capacities of such beams, computed according to the current standards and specifications, ranged from unconservative to overconservative, when compared to those obtained from the finite element analysis and the proposed design model.