Web Crippling Behaviour of Cold-Formed High-Strength Steel Unlipped Channel Beams Under Interior-Two-Flange Load Case

Cold-Formed Steel (CFS) sections are vulnerable to certain local and global failures, especially web crippling failures. CFS beams are generally employed in construction practices mainly as floor joists or bearers. The design standards, AISI S100, AS/NZS 4600 and Eurocode 3 Part 1-3 predict the web crippling capacity of CFS sections according to the experimental studies conducted in previous years. In most of the cases, the predictions of the equations were unsafe and hence innovative concepts of CFS should be examined undergoing web crippling. Therefore, the web crippling behaviour of the unlipped channel sections with high-strength material under Interior-Two-Flange (ITF) loading condition was investigated in this study by following the AISI S909 standard test method defined for web crippling. Numerical simulations using Finite Element Analysis (FEA) software (ABAQUS) were conducted on 243 parametric studies to replicate the loading conditions of ITF following a proper validation. Parametric study data were then taken into account to determine the accuracy of existing equations for web crippling capacity in the design standards and existing literature. Since the available design equations were conservative or unsafe and considering the empirical nature of CFS sections in terms of web crippling capacity, new modified equations were proposed to predict the ultimate web crippling capacity of high-strength unlipped channel sections and a new design approach based on the Direct Strength Method (DSM) was also developed.