Behaviour of Cold-formed Steel Back-to-Back Channel Built-Up Sections under Bending

Abstract

Abstract Cold-formed steel (CFS) structures have been widely constructed as main elements in light structures. In terms of increasing capacity, the built-up sections of cold-formed steel are used regarding larger span structure. In this study, nine cold-formed steel with back-to-back built-up section specimens with various thicknesses were experimentally investigated under three points bending scheme to obtain their capacity and failure type. Each specimen was assembled by using self-drilling screws in web of two built-up channels. Experimental results show that three various web thicknesses (1.3 mm, 1.5 mm, and 2.00 mm) in cold-formed steel of built-up section give the different moment capacity up to 22%. Then, failure types in all specimens are similar where local buckling is generated in compression flange around loading area and lateral-torsional buckling occurred along span. It is found that web thicknesses in back-to-back section have contribution to increase the stiffness and torsional rigidity. However, there is phenomenon when the load capacity decreased, the back-to-back sections act non-composite. Then, the failure apparently observed on that section is one-side twisting and web crippling in mid-span.