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Made using rolled, welded or reticular steel beams designed to
bear the tensile and shearing stresses. Normally, a corrugated steel sheet is laid
over the structure to act as bending reinforcement and provide the form for the
subsequent composite concrete cast designed to bear the compressive stress. The
function of the riveted connectors is to prevent the sliding of the two materials.
The shear connectors can be fastened according to the shear diagram or distributed
more closely near the supports and more thinly in the middle of the composite beam.
The chemical composition of the existing iron beams makes it
difficult, if not impossible the welding of common connectors, because of the
chemical composition of the steel and the presence of rust and mortar layers: the
cold fastening with the TECNARIA connector efficaciously solves the problem, since
the
nails penetrate directly into the steel.
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Between the end of the 19th century and the first half of the
20th century there was
a frequent use of " double T-shaped" beams with interposed bricks for the slab
constructions. The structure was covered with a layer of lean mix for fill, designed
to level the surface of the floor and form the bedding for the flooring.
These floors often require structural
consolidation work as they are designed
to carry moderate loads. An overlayed concrete slab, approximately 5 cm thick,
reinforced with a welded wire mesh and fastened to the load bearing steel beams
using the TECNARIA connectors, enables the adaptation of these structures to the
actual construction requirements.
The interposition of the connectors
between the two elements inhibits slipping and forms a section where, as a result of
the vertical loads, the steel is tensioned, while the concrete is compressed.
The resulting composite structure exploits the peculiarities of the two materials,
enhancing the performance of the floor in terms of strength as well as rigidity. The
process consists of exposing the beam extrados, fastening the connectors, laying a
suitable wire mesh and casting the concrete.
Shoring the floor before the concrete layer is cast ensures that the composite
section is active both as regards the weight of the structure itself and of the
subsequently applied loads.
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Composite structures:
