EXPERIMENTAL STYDY OF TWO-WAY REINFORCED CONCRETE SLAB SUBJECTED TO FIRE IN A STEEL-FRAMED BUILDING

The specially designed furnace was used, and the experiment of two-way concrete slabs in a full-scale three-storey steel-framed building under the combined effects of constant loading and fire were investigated. This paper introduces the design of the test building and furnace, measuring contents and methods. The cracking and failure characteristics of the slab are described. The distribution of temperature along the depth of the slab, the temperature variation of the steel reinforcement, vertical deflection and horizontal displacement are studied. It is shown that the distribution of temperature along the slab depth was nonlinear, and the temperature gradients were large. Under the combined effects of constant loading and fire, intensive cracks occurred on the top of the heated slab along the edges, and plastic hinge lines of circular shape appeared finally. Because of the structural continuity and interaction between structural members, regular cracks also occurred on the top of the adjacent unheated slabs. The vertical deflection of the slab was approximately symmetric during the test, and the largest vertical deflection occurred at the centre of the slab. Due to the high lateral restraint provided by the adjacent unheated structural members, the horizontal displacements at the edges of the slab were not outward but always inward with the increase of the vertical deflection of the slab. The test results indicate that the two-way concrete slab in a whole structure had a good fire performance.