Influence of coefficient of thermal expansion on steel frame strength

The purpose of this paper is to investigate the magnitude of the possible error that could be introduced by assuming the coefficient of thermal expansion for steel is constant for all temperatures. In this paper the basic equation governing the determination of the elastic buckling load factor as a thermal problem is presented. The effects of elevated temperature on the behaviour of steel elements are modelled according to the requirements stipulated in AS4100. A comparison is made of the various limiting temperatures for structures subject to fire using different approximations for the coefficient of thermal expansion recommended by the ECCS and BISRA. Conclusions are drawn as to the acceptability of the assumption of using a constant coefficient of thermal expansion with regard to elastic critical load analysis.