Behaviour of axially-restrained slender steel tubes exposed to fire

The behaviour of axially-restrained slender steel tubes exposed to fire was studied. Fire tests and corresponding finite element (FE) simulations were conducted on four specimens with varying slenderness ratios and axial restraint stiffness. The accuracy of FE simulation was validated against the test results. Both the test and nu-merical results showed that the axially-restrained slender steel tubes buckled at much lower temperatures than steel columns. Continuous temperature elevation was then required to complete their buckling, because the steel maintains considerable stiffness at the buckling temperature. Parametric analysis was conducted based on FE simulations to investigate the effect of the slenderness ratio, axial restraint stiffness, and peak temperature on the behaviour of axially-restrained slender steel tubes exposed to fire. Empirical equations were established for the buckling temperature and post-fire residual lateral displacement using response surface methodology. These equations demonstrated a strong ability to fit the experimental data and predict the responses for new scenarios.