Zhan-Fei Huang

Rankine approach for fire resistance of axially-and-flexurally restrained steel columns

Traditionally, the Rankine equation has been applied to investigate the load bearing capacities of steel columns or frames at room temperature. Recently, the method has been extended to predict the fire resistance of a simply supported steel column by taking the temperature effects on steel material into consideration. This paper further extends the Rankine equation to predict the fire resistance of an isolated steel column from the surrounding structure. The complicated boundary restraints contributed by the adjoining structure are represented by a linear spring and a pair of rotational springs attached to the column ends. Both the boundary restraints and creep strain are incorporated into the Rankine equation. The predictions of Rankine approach are verified experimentally and numerically. Generally, it is shown that under different external load utilization factors and boundary restraint levels, Rankine approach yields accurate and slightly conservative predictions.

Primary creep buckling of steel columns in fire

Abstract This paper proposes an analytical method to predict the fire resistance of a pinned-pinned steel column. Traditionally, the column fire resistance is determined through the standard ISO834 fire test. Under this condition, the external load is kept constant while the member temperature rises monotonically. The complicated creep strain, as well as the degradation of steel mechanical properties is taken into account in this approach. The predictions are verified experimentally and numerically. The extensive numerical verifications show that under different external load levels and different slenderness ratios, the proposed analytical method yields accurate predictions. The procedure can be incorporated into spreadsheet application software.

STRUCTURAL RESPONSE OF A STEEL BEAM WITHIN A FRAME DURING A FIRE

The paper studies the general behavior of a thermal strained steel beams under a fire condition. The governing factors under consideration comprise the load utilization factor, slenderness ratio and axial restraint ratio. Numerical analyses demonstrate that instead of the load utilization factor, it is beam axial restraint that substantially influences the response of beam towards the end of heating. This is due to the catenary action that is experienced by all beams under study. Most importantly, numerical study shows that the deflections which develop under an increasing temperature, are not controlled by the steel material degradation, but by member axial restraint. At very high temperature, the plastic and creep strain in together with post-buckling large displacement, retard the failure of a restrained beam.