Web Crippling Investigation of Cold-Formed Stainless Steel Joist Beams with Web Perforations

Web crippling is a critical failure mode that can significantly compromise the structural integrity of Cold-Formed Steel (CFS) joists, especially when subjected to concentrated loads. This thesis aims to address the critical research gap in the reliability of design equations for predicting web crippling strength on Cold-Formed Stainless Steel (CFSS) floor joist structures, particularly those with web perforations. Despite the widespread use of this Light-Gauge Steel (LGS), due to its superior structural, aesthetic and resistive properties, the existing design specifications have shown significant inaccuracies in predicting web crippling strength. This research evaluates these discrepancies and proposes essential modifications to improve the reliability of design strength equations, for web crippling failure mode involving web perforations, ensuring safer and more efficient structural applications. To achieve this, a detailed experimental investigation was conducted on forty-eight Cee-shaped joist specimens, both with and without perforations, subjected to Interior-One-Flange (IOF) and Interior-Two-Flange (ITF) loading conditions. The experimental data was then validated through numerical analysis using the ANSYS Finite Element Analysis (FEA) package. This dual approach ensured a comprehensive assessment of the web crippling behaviour. The experimental and numerical results were meticulously compared against the prediction made by existing theoretical design specifications specified in the American Iron and Steel Institute (AISI), British Standards (BS) and European Standards (EN). The findings of this research reveal a significant discrepancy between theoretical predictions and actual web crippling strength, thereby emphasising the need for revised design equations. The proposed modifications for reduction factor aim to bridge the gap offering more accurate and reliable guidelines for engineers and designers, for joist members with perforations. By improving the predictive accuracy of these equations, this thesis contributes to the advancement of more reliable Cold-Formed Stainless Steel (CFSS) structures supporting their wide adoption in modern construction practices.