Web crippling design rules for sigma sections under end one flange load case: A numerical study

This study presents a comprehensive numerical investigation into the web crippling behaviour of cold-formed sigma sections subjected to the End One Flange (EOF) load case, a configuration that has received limited attention in existing literature. A total of 756 finite element models were developed using ABAQUS/CAE 2020, covering a wide range of geometric parameters and material types, including carbon steel, aluminium, and stainless steel. The models were validated against experimental data, achieving strong correlation with mean test-to-FE ratios of 1.03, 1.00, and 1.01 for carbon steel, aluminium, and stainless steel, respectively. The results revealed that web crippling capacity decreases by up to 35% with increasing section depth and radius, while yield strength enhancements of up to 60% significantly improve capacity. Stainless steel sections consistently outperformed the other materials under identical geometric and loading conditions due to their superior strain-hardening characteristics. Existing design standards (AS/NZS 4600, AS/NZS 4673, and AS/NZS 1664) were found to inadequately predict the web crippling strength of sigma sections. Consequently, two unified design equations were proposed by modifying existing formulations, achieving mean prediction ratios of 1.00 with COVs below 0.11 across all materials. A reliability analysis confirmed the robustness of the proposed equations, recommending a resistance factor of 0.85. These findings provide a validated and practical design framework for predicting the web crippling capacity of sigma sections under EOF loading, supporting their broader application in structural engineering.