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Structural Steel Frames 339
rating, the underside of the deck can be coated with sprayed-on protection or an intumescent
coating. Where there is to be a flush ceiling for appearance and as a housing for
services, a suspended ceiling is hung from hangers slotted into the profile or hangers bolted
to the underside of the deck.
For particularly large spans or where cuts are made through the profile metal sheet for
services, some temporary propping is required until the concrete has reached its 7 day
maturity.
Slimfloor floor construction
‘Slimfloor’ is the name adopted by British Steel (now Corus) for a form of floor construction
for skeleton steel-framed buildings. This form of construction is an adaptation of a
form of construction developed in Sweden where restrictions on the overall height of buildings
dictated the development of a floor system with the least depth of floor construction
to gain the maximum number of storeys within the height limitations. Slimfloor construction
comprises beams fabricated from universal column sections to which flange plates are
welded, as illustrated in Figure 5.60. The flange plates, which are wider overall than the
flanges of the beams, provide support to profiled steel decking that acts in part as reinforcement
and provides support for the reinforced concrete constructional topping. The galvanised,
profiled steel deck units are 210 mm deep with ribs at 600 mm centres. The ribs and
the top of the decking are ribbed to stiffen the plates and to provide some bond to concrete.
To seal the ends of the ribs in the decking, to contain the concrete that will be cast around
beams, sheet steel stop ends are fixed through the decking to the flange plates, as illustrated
in Figure 5.61. Constructional concrete topping is spread over the decking and into
the ribs around reinforcement in the base of the ribs and anti-crack reinforcement in the
floor slab.
The galvanised pressed steel deck units are designed for spans of 6 m for use with the
typical grid of 9 m beam spans at 6 m centres. For spans of over 6 and up to 7.5 m,
the decking will need temporary propping at mid-span until the concrete has developed
Cross section
Universal section (beam)
Flange plate welded to beam
Figure 5.60 Slimfloor beam.