Buckling and Critical Temperature Prediction Formulas of Restrained H-Section Steel Columns in Fire

Buckling and critical temperatures of steel columns are crucial parameters for structural fire safety design. However, the existing simplified design methods for buckling or critical temperature are based on column models with either pin ends or with large rotational restraints. Their applications on steel columns with limited rotational restraint stiffness ratios—the ones smaller than the critical rotational restraint stiffness ratio—is questionable. In this paper, parametric analyses on a validated numerical column model with rotational restraint stiffness ratio varying from 0.0001 to 10.0 were conducted. The effects of slenderness ratio, load ratio, and axial restraint stiffness ratio were also considered. Results show that for steel columns with limited rotational restraint stiffness ratios, prediction errors of existing simplified design methods were significant. Following the parametric analyses, new prediction formulas of buckling temperature and critical temperature are proposed for H-section steel columns. Results of proposed formulas aligned closely with those of parametric analyses in the full range of considered parameters. Furthermore, the proposed formulas were also validated by test results in the literature.