Structural response of restrained steel columns at elevated temperatures. Part 2: FE simulation with focus on experimental secondary effects

This paper presents finite element simulations of a series of elevated temperature tests on axially-restrained steel columns conducted at Nanyang Technological University. The test results have been presented in the companion paper (Part 1), which also includes analytical predictions of failure times based on the Rankine formula extended to the elevated temperature case. The columns with different axial restraint ratios were subjected to a constant axial load ratio. This paper focuses on accurate simulation of secondary effects arising from the experiments, namely, initial crookedness and boundary friction. An approach to correctly ascertain the axial restraint stiffness and rotational restraint stiffness due to inevitable friction effects is discussed in detail. Good agreement between FE predictions and experimental results on column internal force and lateral displacement validates the proposed numerical approach. In addition, the effects of load eccentricity, boundary friction and steel material models on column failure time are also examined. These effects are shown to have significantly influenced the structural response of heated columns.