Experimental and numerical investigations of cold-formed austenitic stainless steel unlipped channels under bearing loads

While mechanical properties and material stress-strain response of different families of stainless steel (known as austenitic, duplex and ferritic) are different from each other, current cold-formed stainless steel standards do not generally take into account these differences as they provide single equations for any loading scenario to cover all groups of stainless steel. This may lead to inaccurate results, especially for austenitic steel which is a high performance material increasingly used in modern construction, due to its higher ductility and ultimate-to-yield strength ratio. This research aims to investigate the web bearing performance of cold-formed steel channels fabricated with austenitic stainless steels subject to concentrated transverse forces experimentally and numerically. The experimental programme consists of 16 thick unlipped channel specimens with different internal fillet radius and web depth to thickness ratios. For the numerical investigations, 88 detailed nonlinear quasi-static finite element models are used and validated against experimental data. Complementary parametric investigations are then conducted to ascertain the web bearing strengths in terms of various channel sizes, web thicknesses and internal fillet radius. It is found that the equations proposed by current stainless steel standards are unreliable for austenitic steel as they can lead to significantly un-conservative results (up to 43%) under both one- and two-flange loading scenarios. Other equations suggested in the literature for ferritic stainless steel are also shown to provide overestimated results (up to 34%) for austenitic steel channel sections. Based on the experimental and analytical results from this study, new equations are proposed to estimate the web bearing strength of cold-formed austenitic stainless steel channels and their reliability is demonstrated.