Effect of axial restraint on the performance of Elliptical Hollow Section steel columns, in hydrocarbon fire

This paper presents the findings from a novel experimental programme that examines the influence of axial restraint on the loading and buckling capacity of Elliptical Hollow Section (EHS) steel columns, when exposed to the hydrocarbon fire curve. When fire occurs in a structure, the steel columns are subject to thermal expansion, and in practice this thermal expansion is normally restrained by the cooler surrounds of the structure. Restraining this thermal expansion, subsequently introduces restraint forces, which are not present in the structural element prior to heating. This experimental programme comprised of 12 EHS column tests of two slenderness λ z = 40.1 and λ z = 50.8 , under three different loading levels ( α L = 0.3 , 0.45 and 0.6), exposed to a hydrocarbon heating regime. Initially, six EHS columns were tested unrestrained followed by six restrained EHS column tests. The fire resistance of the restrained columns were subsequently compared with the previous unrestrained column tests, tested under the same mechanical and thermal loading conditions. This paper will provide the recorded axial displacements, temperature profiles and induced axial forces of the restrained EHS columns, comparing these findings with the unrestrained EHS columns.