Shallow Metal Deck Floor Construction.

Experience has shown that the most efficient floor arrangements are those using shallow metal decking spanning about 3–4.5m between floor beams. For these spans the metal decking does not normally require propping during concreting and the concrete thicknesses are near the practical minimum for consideration of strength and fire separation.

Steel studs are welded through the decking on the flange of the beams below to form a connection between steel beam and concrete slab. Concrete, which may be either lightweight or normal weight, is then poured on to the decking, usually by pumping, to make up the composite system. Shallow metal decking acts both as permanent formwork for the concrete and as tensile reinforcement for the slab. There are many types of steel decking available (Fig. 2.25(a)) but perhaps the most com- monly used is the re-entrant profile type, which provides a flat soffit and facilitates fixings for building services and ceilings.

Metal deck profiles: (a) shallow deck (50–100mm); (b) deep deck (150–250mm)
Fig. 2.25 Metal deck profiles: (a) shallow deck (50–100mm); (b) deep deck (150–250mm)

Some of the advantages of composite shallow metal deck floor construction are:

• Steel decking acts as permanent shuttering,which can eliminate the need for slab reinforcement and, due to its high stiffness and strength, propping of the con- struction while the wet concrete develops strength.
• Composite action reduces the overall depth of structure.
• It provides up to 2 hours fire resistance without additional fire protection and 4 hours with added thickness or extra surface protection.
• It is a light, adaptable system that can be easily manhandled on site, cut to awkward shapes and drilled or cut out for additional service requirements.
• Lightweight construction reduces frame loadings and foundation costs.
• It allows simple, rapid construction techniques.

Figure 2.26 illustrates alternative arrangements of primary and secondary beams for a deck span of 3m.

Alternative framing systems for floors: (a) long span secondary beams; (b) long span primary beams
Fig. 2.26 Alternative framing systems for floors: (a) long span secondary beams; (b) long
span primary beams

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