Buckling improvement of pretwisted universal steel beams

Beams are structural components that are mainly utilized to resist flexure. However, beam sections are also commonly used to resist axial tension and compression in certain situations such as when they are used as truss members or braces. Pretwisting compression members strengthens their weak flexural plane and weakens their strong flexural plane, leading to an overall improvement in the buckling capacity. In this paper, pretwisting is applied to structural steel UB100 × 50 × 9.3 beam sections, both experimentally and numerically using finite element (FE) analysis, in an attempt to improve their critical buckling capacity. The experimental study consists of fourteen specimens of three different lengths and a variety of pretwist angles, while the linear-perturbation FE analysis considers ninety-one specimens of eight length groups and a pretwist angle range between 0° and 180°. In both studies, it was found that pretwisting improves the critical buckling capacity of UB100 × 50 × 9.3 beams. The linear-perturbation analysis also showed that the length of the members has no effect on the buckling capacity improvement, and that this improvement is highly significant under fixed-fixed end conditions but not under pinned-pinned conditions.