Mechanical properties of cold-formed steel cladding profiles at elevated temperatures

Cold-formed steel (CFS) claddings are increasingly used in bushfire prone areas in Australia due to their non-combustibility and are recommended in the Australian standard AS 3959 for the design of buildings in bushfire prone areas. Thus, good knowledge and understanding of their behaviour at elevated temperatures is important for the safe design of buildings. However, the elevated temperature mechanical properties of thin CFS cladding profiles have not been investigated. Hence, this research investigated the elevated temperature mechanical properties of high strength CFS cladding profiles through steady-state tensile coupon tests. More than 100 coupons, taken from the crests of three different cladding profiles with thicknesses of 0.42 mm and 0.48 mm, were tested to failure at predetermined elevated temperatures. The elevated temperature mechanical property results were compared with corresponding results from previous studies conducted on CFS sheets and sections, and the predictions obtained from the Australian CFS design standard. These comparisons showed that currently available equations can be used to determine the elevated temperature stress–strain curves and mechanical properties of CFS cladding profiles except for ultimate and fracture strains. Since no suitable equations are available for ultimate and fracture strains of CFS at elevated temperatures, new equations are proposed for CFS with varying thicknesses.