Civil Engineering Reference
In-Depth Information
Figure 2.8
Composite slab
Bars with hoops are the strongest of these, with ultimate shear strengths
up to 1000 kN. Design rules are given in BS 5400:Part 5 and in the
preliminary Eurocode 4, ENV 1994-1-1, but were omitted from EN 1994-
1-1 because they are now rarely used. Epoxy adhesives have been tried,
but it is not clear how resistance to uplift can reliably be provided where
the slab is attached to the steel member only at its lower surface.
2.4.3
Shear connection for profiled steel sheeting
This material is commonly used as permanent formwork for floor slabs in
buildings, then known as
composite slabs
. Typical cross-sections are shown
in Figs 2.8, 2.14, 2.20 and 3.12. As it is impracticable to weld shear
connectors to material that may be less than 1 mm thick, shear connection
is provided either by pressed or rolled dimples that project into the
concrete, or by giving the steel profile a re-entrant shape that prevents
separation of the steel from the concrete.
The resistance of composite slabs to longitudinal shear is covered in
Section 2.8, and their design in Section 3.3.
2.5
Properties of shear connectors
The property of a shear connector most relevant to design is the relation-
ship between the shear force transmitted,
P
, and the slip at the interface,
s
.
This load-slip curve should ideally be found from tests on composite
beams, but in practice a simpler specimen is necessary. Most of the data
on connectors have been obtained from various types of 'push-out' or
'push' test. The flanges of a short length of steel I-section are connected
to two small concrete slabs. The details of the standard push test of EN
1994-1-1 are shown in Fig. 2.9. The slabs are bedded onto the lower
platen of a compression-testing machine or frame, and load is applied to
the upper end of the steel section. Slip between the steel member and the
