Development of an Axial Load Capacity Equation for Doubly Symmetric Built-Up Cold-Formed Sections

Abstract

This work aims to develop an axial load capacity equation for doubly symmetric built-up cold-formed sections with a sufficient number of intermediate, symmetrical connections. A numerical parametric study involving a total of 360 different configurations was conducted, and the numerical results were compared with the experimental data and specifications from the American Iron and Steel Institute (AISI). In this process, the axial load capacities and failure modes, which were influenced by out-of-straightness and out-of-flatness, were thoroughly investigated. To address the issues of an unnecessarily complicated AISI specification for doubly symmetric members subject to distortional buckling, a simple and reliable axial load capacity equation was developed based on a regression analysis of a three-dimensional surface fitting and calibration with the experimental data. This proposed equation exhibited good agreement with the numerically simulated and experimentally measured capacities, while simultaneously ensuring safety and efficiency.