Web crippling behaviour of sigma sections under end two flange loading – Numerical investigation

Abstract

Cold-Formed (CF) sections have emerged in the construction industry due to their merits, including ease of fabrication for different section profiles, sustainability, and cost-effectiveness. As a result, various innovative section profiles have been introduced to the CF industry. Sigma sections are one such innovative profile that has been introduced in the CF industry. The inclusion of longitudinal stiffeners in Sigma sections improves their bending capacity. Additionally, Sigma sections offer high stiffness, increased torsional rigidity, and superior load-carrying capacity. However, the inclusion of web longitudinal stiffeners might induce localised failures under concentrated loads, known as web crippling failures. Therefore, it is necessary to explore the web crippling behaviour of Sigma sections to effectively employ them in the industry. However, limited research has been conducted on Sigma sections in terms of web crippling. Thus, this research intends to investigate the web crippling behaviour of Sigma sections under the ETF load case. A comprehensive numerical study consisting of 1512 numerical models was conducted on Sigma sections made of aluminium (432 numerical models), carbon steel (648 numerical models), and stainless steel (432 numerical models) after successfully validating the numerical approach. The results obtained from the numerical study were compared using parameters such as section depth, thickness, yield strength, bearing length, and radii. The numerical results were also compared with existing design equations and considering their inaccuracy in predicting the web crippling capacity of Sigma sections made of CF carbon steel, stainless steel, and aluminium under the ETF load case, modified design provisions were proposed. In addition, a numerical investigation was conducted to analyse the web crippling performance of Sigma section with conventional sections, and it was concluded that similar web crippling performance was observed for Sigma sections. Hence, the Sigma sections were highly recommended for extensive applications in the industry.