Unified design equations for web crippling failure of cold-formed ferritic stainless steel unlipped channel-sections with web holes

Abstract

This paper addresses the design of cold-formed ferritic stainless steel unlipped channel-sections with offset web holes and fastened flanges subject to web crippling under one-flange load scenarios. The results of a total of 18 new experimental tests, not reported previously, are presented; these were conducted on ferritic 1.4016 grade unlipped channel-sections under both interior- and end-one-flange loadings. The results are used to validate a non-linear quasi-static finite element model to simulate the behaviour of such sections. A comprehensive parametric study including a total of 576 FE models is then undertaken to determine the web crippling strengths for unlipped channel-sections with different web heights, web thicknesses and location of web holes under both interior- and end-one-flange loadings. In addition, the experimental and FE results are compared against strengths predicted in accordance with the American Iron and Steel Institute (AISI S100-16) for cold-formed carbon steel plain lipped channel-sections as well as the equations proposed in previous studies for stainless steel plain lipped channel-sections. It is found that the current design equations are unreliable and unconservative to use for cold-formed ferritic stainless steel unlipped channel-sections by as much as 22%. To address this issue, based on the results of this study, two new reliable web crippling strength reduction factor equations are proposed for such unlipped channel-sections. The proposed equations should prove useful for practical design of cold-formed ferritic stainless steel unlipped channel-sections with offset web holes and fastened flanges. For practical design application, the equations are then unified by combining the proposed equations with existing equations from the literature to allow a unified design equation to be developed for ferritic stainless steel unlipped channel-sections with centred and offset web holes and with both flanges fastened and unfastened to the bearing plates under one- and two-flange load scenarios.