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Structural Steel Frames 341
The advantages of the slimfloor construction are:
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Speed of construction through ease of manhandling and ease of fixing the lightweight
deck units, which provide a safe working platform
Pumping of concrete obviates the need for mechanical lifting equipment
The floor slab is lightweight as compared with in situ or precast concrete floors
The deck profile provides space for both horizontal services in the depth of the floor
and vertical services through the wide top flange of the profile
Least overall depth of floor to provide minimum constructional depth consistent with
robustness requirements dictated by design codes
Composite construction
Composite construction is the name given to structural systems in which the separate
structural characteristics and advantages of structural steel sections and reinforced concrete
are combined as, for example, in the T-beam system. A steel frame, cased in concrete
and designed to allow for the strength of the concrete in addition to that of the steel, is a
form of composite construction. Where concrete encases steel sections, it is accepted that
the stiffening and strengthening effect of the concrete on the steel can be allowed for in
engineer’s calculations. By reinforcing the concrete casing and allowing for its composite
effect with the steel frame, a saving in steel and a reduction in the overall size of members
can be achieved.
Shear stud connectors
A concrete floor slab bearing on a steel beam may be considered to act with the beam and
serve as the beam’s compressive flange, as a form of composite construction. This composite
construction effect will work only if there is a sufficiently strong bond between the concrete
and the steel, to make them act together in resisting shear stresses developed under load.
The adhesion bond between the concrete and the top flange of the beam is not generally
sufficient, and it is usually necessary to fix shear studs or connectors to the top flange of
the beam, which are then cast in the floor slab. The purpose of these studs and connectors
is to provide a positive resistance to shear. Figure 5.62 is an illustration of typical shear stud
connectors and Figure 5.63 is an illustration of composite floor and beam construction.
30
or
35 mm
20 or 22 mm
diameter
75, 100
or
125 mm
Figure 5.62 Shear stud connector.
Coned end is coated with flux