Fire Behaviour of Long Span Composite Floor

In scope of the ECSC project Steel Intensive Systems for Shallow Floor Construction a fire test is carried out on a two-span composite flooring system of a continuous composite slab using deep deckings supported on integrated steel beams. The system spans approx. 2 times 4x4 m. In terms of mechanical loading, the degree of utilization of the centre beam amounts 0.5. Nevertheless, a fire resistance of more than 90 minutes is reached without fire insulation. The test is simulated successfully with FEM models. First, 2D thermal models are developed for the beam and the slab separately. The effect of thermal shielding of the slab is taken into account. Moreover, the radiative heat exchange between the upper flange and the web of the decks has been considered as well as the reduced contact between the steel sheets and the concrete cover as developed during the test. The structural analysis uses material models accounting for temperature dependent yielding of steel and cracking of concrete. The composite action between the beams and the encased concrete is simulated assuming no slip and applying an effective width of the slab of L/4. KEYWORDS