Influence of rotational restraints on response of H-section steel columns under fire

Abstract

In this paper, a parametric investigation on the influence of rotational restraints on the response of H-section steel columns under fire was conducted through a validated numerical model. Nine rotational restraint stiffness ratios (βR) were considered, from 0.0001 to 10.0. Other considered parameters include the slenderness ratio, axial restraint stiffness ratio, and load ratio. The analysis results showed that there are three failure scenarios of the columns with βR increases from 0.0001 to 10.0. Specifically, in failure scenario I, the failures are all dynamic failures; in failure scenario II, the failures change from dynamic failure to quasi-static failure; and in failure scenario III, the failures are all quasi-static failures. The occurrence of the failure scenarios is related to the slenderness ratio, axial restraint stiffness ratio, and load ratio. The dynamic effects of the columns in failure scenario I decrease first and then increase with the increase of βR. The dynamic effects of the columns in failure scenario II decrease with the increase of βR until the failure type of the columns change to quasi-static failure. For the above failure scenarios, there is a critical value of βR (namely βR,cr), after reaching which the influence of βR on the response of the columns becomes negligible. The value of βR,cr is less than 2.0 in general, and depends on the slenderness ratio, axial restraint stiffness ratio, and load ratio. The failure scenarios and βR,cr values of the H-section columns are the same with box-section columns for most of the cases.