ABSTRACT
Tubular members with intermediate to high slenderness ratios are normally used in space frame structures. When the space frame structure is subjected to localized fire, only part of the structure is subjected to heating and the heated members are restrained by the adjacent members which are not heated. In the second part of this paper, a series of experiments is conducted to investigate the buckling of axially restrained tubular members with initial imperfection under ISO834 fire condition. The parameters to be investigated include load ratio, axial restraint stiffness ratio, member slenderness ratio and initial out-of-straightness on the fire resistance of axially restrained members at the buckling and post-buckling stage. Eight tubular specimens with different cross section areas and end restrained stiffness were tested under standard ISO834 fire up to a maximum temperature of 800°C. The tests show that the member buckling during the heating and the buckling temperature decreased with the increase of load ratio, slenderness ratio and axial restraint stiffness. It is worth noting that the buckling temperature increased slightly with the increase of initial lateral imperfection. The post buckling resistance of the axially restrained members can also be determined. The tests show that the post buckling resistance increases with the increase of axial restraint stiffness. With the increase of axial restraint stiffness ratio, the permanent deflection of the members decreased when they cool down to the ambient temperature.
