Numerical analysis of cold-formed steel built-up closed sections subjected to axial load.

Cold-formed steel (CFS) is frequently utilized in construction owing to its lightweight, ease of production, straightness, and durability. These properties make CFS an ideal choice for various structural applications, including framing, roofing, cladding systems, straightforward quality control, and cost-efficient transportation compared to traditional materials. It also allows for the flexible design of cross-sectional profiles and is fully recyclable. This study presents a numerical analysis of built-up columns fabricated from cold-formed steel. Four built-up steel columns were tested, differing in thickness (1 mm and 2 mm) and length (1200 mm and 2000 mm), under pin-ended boundary conditions. The cross-sections are manufactured by composing two identical zee sections and channels using self-tapping screws. The specimens were modeled using ABAQUS software, incorporating material properties and geometric imperfections into the finite element (FE) models. The results of the numerical simulations closely matched previous experimental findings for built-up closed columns subjected to compressive loads, thus validating the FE model. The study revealed that axially loaded columns with varying slenderness ratios exhibited different failure modes, including local buckling, local-flexural buckling, and flexural-distortional buckling.