ABSTRACT
It is not a general practice to apply re protection to the soft of a composite slab. This means that the prole sheet steel decking is exposed directly to a re and therefore loses its strength very rapidly. Furnace tests revealed that simply supported composite slabs are inherently capable of providing 30-min re resistance when exposed to the standard furnace test, and the decking may be assumed to retain about 5% of its original strength (Cooke et al., 1988). However, most calculation methods are conservative in ignoring this residual strength and determine the strength of the slab system purely on contributions of the concrete slab and any exural reinforcement. As with reinforced concrete construction, the slab is required to satisfy both the load-bearing capacity and insulation limit states. The latter is generally satised by specifying overall slab depths.
