doi:10.3850/978-981-08-9247-0_rp067-icsas11

ABSTRACT

A 3D finite element model incorporating both geometric and material non-linearity is created to investigate the behaviour of a cold-formed Z-shaped steel purlin in fire. It has been shown that as a result of the thinness of the material and degradation of material properties at elevated temperature, the profile buckles locally under restrained thermal expansion at an early stage. When large deformation took place, tensile forces developed in steel purlins to resist a transversely applied load. A steel purlin can survive in fire because of catenary action. Compared to a one-span purlin, two-span purlins have less in-web-plane deformation because of the existence of mid-support but greater out-of-web-plane deformation because of their sudden lateral-torsional buckling. The earlier inelastic buckling at the two end supports in a one-span purlin actually helps to reduce the compressive forces developed at end supports. However, when the purlins are in catenary action, the maximum axial tension forces developed at the supports are the same for both one-span and two-span purlins.

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