Part 1: Architect’s Guide 1 - 23 Permanent formwork (Non composite slab) Composite slabs (Steel deckings with embossments) Figure 4.13 Concrete slab with steel decking To optimize structural behaviour, a composite slab with steel decking can also be designed to contribute to the bending resistance of the beams (composite beams), as shown in Figure 4.14. This leads to a reduction in the size of the steel profiles, and subsequently in the total depth of the floor, the weight of the beam, etc. Typical dimensions of a steel decking: Length: 6 m Width: 1 m Thickness: 0,75 or 1 mm. Figure 4.14 Composite slab and composite beams Fire resistance of slabs composed of a steel decking and concrete The steel decking has a mechanical function of reinforcement. The underside generally requires no protection. The composite slabs can have 30 minutes’ fire resistance without special protection. A higher resistance can easily be obtained by: Adding reinforcement bars in the slab Protecting the underside of the decking Adding a false ceiling of mineral wool and plasterboard.
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