Effects of external bending moments and heating schemes on the responses of thermally restrained steel columns

This paper investigates the effects of both external moment and different heating schemes on thermally restrained steel columns. Only the cross-sectional uniform heating profile is studied. A self-developed finite element program FEMFAN is applied in this study. The first part of the paper investigates the developments of column internal forces as well as cross-sectional stresses and strains for a heated column subjected to both external axial load and two moments acting on opposite ends. It shows that such external moments can significantly reduce the critical temperature of pin-roller columns, while they have very limited effect on rotationally restrained steel columns due to the moment restoring effect. Thus, for typical rotationally restrained steel columns, the external moment need not be included in the calculation of the load utilisation factor, when calculating the column critical temperature. The second part of the paper studies the effects of both rapid and slow heating schemes on column critical temperature. Creep is found to dominate the column behaviour beyond 450 °C, and under a slower heating rate.