Buckling behaviour of steel columns under elevated temperature

Abstract

This paper presents experimental investigations on the behaviour of steel columns under elevated temperature. Axial restraints were applied to simulate the real-time boundary conditions, being part of a steel-framed structure. In the present study, two specimens, namely ISMB200-H1 and ISMB200-H2 were exposed to elevated temperature conditions by using 24kW and 7kW heaters respectively. The heating was carried out from room temperature to 800°C gradually, under a constant axial load applied through a specially fabricated loading frame. The critical temperature was estimated based on the point at which the specimen could no longer withstand the applied load. The applied load was significantly influenced by axial restraint, wherein additional stress was generated due to restrained thermal elongation in the axial direction. Two types of failures were observed at the end of experiments, namely (i) local mode of failure in the specimen ISMB200-H1 and (ii) global mode of failure in specimen ISMB200-H2 due to temperature concentration (maximum temperature) at top end plate and mid-height of the specimens respectively. The analytical studies were carried out with the expressions available in BS EN 1993-1-2, IS800:2007 and CSA S16:19 to have an understanding on load carrying capacity with increase in temperature. It is inferred that analytical studies provided comparable results on the load-bearing capacity of the specimen ISMB200-H2, which has failed by global mode.