Mechanical Behaviour of the Cold-formed Steel Channel Stub Column Under Post Elevated Temperature

Abstract

Cold-formed steel (CFS) is the popular structural material used in the building nowadays due to a variety of advantages in its manufacturing, fabrication and erection. CFS with the shape of the channel is selected and formed to be a stub or short column with a height of 240mm. The main objective of the study is to determine the mechanical behaviour of the CFS channel stub column at post elevated temperature from normal to 1000 0C. The CFS stub columns are exposed to fire at the furnace and let it cool at room temperature. After 24hours, the CFS is tested by using Universal Testing Machine (UTM) for ultimate load. When this material is exposed to fire the steel material properties are degraded. The strength of the CFS stub column is recovered to its original normal strength when heated below 600°C; beyond this temperature the strength has reduced with recovery of strength less than 65%. It was observed the column would fail by a combination of local and some distortional buckling. The predictions using Direct Strength Method (DSM) are conservative for all post elevated temperature of the CFS stub column and the column were predicted to fail by distortional buckling. The CFS channels are able to remain the strength after exposing to temperature up to 400°C. Beyond that, the capacity was reduced more than 40% of the normal strength. The prediction with the EC3 yield for temperature up to 400°C the prediction is overdesigned and considerably unsafe. But beyond temperature of 400°C, it was conservative similar to the Direct Strength Method. The columns are predicted to fail in compression failure.