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336 Barry’s Advanced Construction of Buildings
Photograph 5.16 Steel deck ‘wriggly tin’ floor.
Profiled cold-rolled steel decking, as permanent formwork, acting as the whole or a part
of the reinforcement to concrete, has become the principal floor system for structural
steel frames (see Photograph 5.16, Photograph 5.17, Photograph 5.18 and Photograph
5.19). The profiled steel deck is easily handled and fixed in place as formwork (centring)
for concrete. The profiled cold roll-formed, steel sheet decking, illustrated in Figure 5.59,
is galvanised on both sides as a protection against corrosion. The profile is shaped to bond
to the concrete, using projections that taper in from the top of the deck. Another profile is
of trapezoidal section with chevron embossing for key to concrete. The steel deck may be
laid on the top flange of beams, as illustrated in Figure 5.59, or supported by shelf angles
bolted to the web of the beam to reduce overall height and fixed in position on the steelwork
with shot fired pins, self-tapping screws or by welding, with two fixings to each sheet.
Side laps of deck are fixed at intervals of not more than 1 m with self-tapping screws
or welding.
For medium spans between structural steel beams, the profiled steel deck acts as
both permanent formwork and as reinforcement for the concrete slab that is cast in situ on
the deck.
A mesh of anti-crack reinforcement is cast into the upper section of the slab, as illustrated
in Figure 5.59. For long spans and heavy loads, the steel deck can be used with additional
reinforcement cast into the bottom of the concrete between the upstanding profiles and,
for composite action between the floor and the beams, shear studs are welded to the beams
and cast into the concrete. The steel mesh reinforcement cast into the concrete slab floor
is sufficient to provide protection against damage by fire in most situations. For high fire