Web-Crippling Capacity of High Performance Cold-Formed Lipped Steel Sections Subjected to Elevated Temperature

High-performance steel has emerged as an advanced structural material in the construction practice of industrial buildings, due to its excellent properties. However, fire poses a significant threat to cold-formed steel structures, as they are prone to deform and buckle under the exposure, potentially leading to building collapse. This study aimed to evaluate the post-fire web-crippling behaviour of high performance CFS sections for End Two Flange (ETF) and Interior Two Flange (ITF) load cases. Two types of specimens were used: CFS webs without holes and CFS webs with circular holes. All test specimens were heated according to the ISO 834 standard fire curve and were subsequently cooled by air or water. A total of 52 specimens (ambient and post-fire) were tested under ETF and ITF load conditions. The load-deflection behaviour and failure modes were evaluated through experimental and numerical analysis. Finite element modelling was used to compare the load-deflection behaviour and failure modes of CFS members with experimental results. The experimental results indicate that the web load-carrying capacity of the high-performance steel member decreases drastically as the heating duration increases. Furthermore, the ITF load case specimens exhibited a lower strength loss than the ETF load case specimens at elevated temperatures. There was an excellent agreement between the experimental and FEM results in terms of the load-carrying capacity and failure modes of high performance CFS.