Behaviour of precast concrete floor slabs exposed to standardised fires

This paper quantifies the thermal movements of 14 simply supported precast reinforced concrete floor slabs of 4.5 m span and 900 mm width exposed to two standardised heating regimes used in fire resistance furnace tests. The tests were designed to show the effect of varying the slab thickness, type of concrete, imposed load, soffit protection and nature of fire exposure on the mid-span flexural deflection and axial movements of the slab ends. Measured deflections showed that during the 90 min design period of fire resistance thermal bowing was dominant and the effect of the 1.5 kN/m 2 design imposed load was small. The NPD hydrocarbon fire exposure caused a doubling of the flexural deflections achieved using the standard BS 476: Part 8 (now Part 20) fire exposure in the first 20 min of exposure.