Failure temperatures of steel H-section columns under elevated temperatures

This paper introduces the failure temperatures and stresses of H-section columns under elevated temperatures. The failure tests using the heating furnace were performed at the Fire Insurers Laboratories of Korea. The eight specimens fabricated of SS400 steel were tested and the slenderness ratio, the width-thickness ratio of the flange, and the width-thickness ratio of the web of all specimens were fixed at 45.4, 10.0 and 26.4, respectively. The specimens loaded by constant compression were heated until failure occurred. Four types of compressive stresses were selected as initial loading conditions;, these compressive stresses corresponded to 50, 60, 70, and 80% of the yield strength at ambient temperature. The specimens are classified into four groups according to the initial compressive stress. The compressive stresses which are initially loaded in the tests are also defined as the failure stresses at the failure temperatures of specimens. The failure stresses are compared with the linear elastic and nonlinear buckling stresses and the yield stresses (which respond to the failure temperatures) by using the Eurocode 3 Part 1.2 which defines the material property of steel under elevated temperatures. The linear local and overall buckling stresses were higher than the yield stresses at the failure temperatures and the failure phenomenon was caused by nonlinear buckling occurring before yielding failure. The failure stresses were lower than the yield stresses obtained by the EC3 at the failure temperatures. The failure stress ratios of the four groups of specimens loaded as 50, 60, 70, and 80% of ambient yield strength were evaluated as 0.78, 0.89, 0.88, and 0.92 of the yield stresses given in EC3, respectively. The nonlinear buckling stresses defined by EC3 showed about 0.65 of the failure stresses. The four groups of specimens failed at 543.5, 534.5, 489.9, and 457.9A degrees C, respectively.