Strength and buckling of cold-formed steel laterally unbraced stiffened C and Z sections

Abstract

The ultimate strength and buckling behaviour of cold-formed steel (CFS) laterally unbraced stiffened C and Z section members in bending and torsion were investigated. Bending tests were conducted on CFS beams with five different stiffener combinations (web, flange or a combination of web and flange intermediate stiffeners). The experimental and numerical results showed a reduction in displacement and an increase in bending strength after the provision of intermediate stiffeners along the web and flange of the channel members while there was an increase in both buckling loads and displacement in the Z sections. Flexural and lateral torsional buckling was predominant in simple end stiffened and single web stiffened sections, while sections with combined web and flange stiffeners failed due to combined distortional, flexural and lateral torsional buckling. The experimental results were simulated using finite-element software and they showed good agreement with the experimental results in terms of displacement, bending strength and buckling modes. CFS members can be plain in simple applications, but if provided with flange or web intermediate stiffeners, their performance and resistance to buckling improves. The idea behind this study was to use CFS members with a modified shape rather than thickness to carry extra load. Due to the relatively easy manufacturing method, a large number of different configurations can be produced to fit the demands of optimised designs for both structural and economic purposes.

Web–flange distortional buckling of partially restrained CFS beams under uplift loading

“…It is well known that beams made from cold-formed steel (CFS) can buckle in the form of local buckling (LB), distortional buckling (DB), or lateral-torsional buckling (LTB) (Hancock, 1978;Li, 2011;Selvaraj and Madhavan, 2019;Yerudkar and Vesmawala, 2018) because of their opensection and thin-thickness nature. In general, the design load of short-span CFS beams is controlled by the LB and DB; whereas that of long-span CFS beams is controlled mainly by the LTB.…”