Numerical analysis and design of cold-formed steel elliptical hollow sections under combined compression and bending

This paper aims to study the structural performance and design of cold-formed steel elliptical hollow sections under combined compression and minor axis bending. An accurate finite element model was developed and validated against the available test results. The validated model was further used to carry out an extensive parametric study on 560 beam-columns, including fifty-six cross-section series with two different specimen lengths loaded at five different eccentricities, and 112 concentric loaded column counterparts. A broad range of cross-section geometries and a spectrum of member slenderness and loading eccentricities were designed for the parametric study. A total of 602 beam-column results, including 42 available test data and 560 numerical results in this study was compared with the predictions by the existing design methods, such as the equivalent diameter method and the equivalent rectangular hollow section approach with the European Code as well as the existing traditional design rules (Australian Standard, North American and American Specifications) using equivalent diameter. Reliability analysis was also carried out. It is shown that the existing design methods provide quite conservative and scattered design strength predictions. In this study, modifications are proposed on the Australian Standard, North American and American Specifications, which are proven to provide accurate and reliable design predictions. Among the three modified design methods, it is recommended to use the modified ANSI/AISC360 method for the design of cold-formed steel elliptical hollow sections under combined compression and minor axis bending as it provides the most accurate predictions in this study.