Simply-supported composite slabs and beams - Composite Structures of Steel and Concrete - page 54

design value, τ u,Rd . (This is where the greater effect of friction in short

spans is neglected.)
At an end support, the bending resistance of the slab is that of the
sheeting alone (unless it is enhanced by the use of end anchorage, as
described later). At any cross-section at distance x from the support, the
compressive force in the slab can be calculated from τ u,Rd . This force may

optionally be increased by is a coefficient of friction and

R Ed is the support reaction. The partial-interaction method of Section
3.3.1(3) enables the bending resistance, M Rd , at that cross-section to be
calculated. There may be a mid-span region where full shear connection
is achieved and M Rd is independent of x .
For safe design, this curve of M Rd as a function of x (the resistance
diagram) must at all points lie above the bending-moment diagram for the
applied loading. If the loading is increased until the curves touch, the
position of the point of contact gives the location of the cross-section of
flexural failure and, if the interaction is partial, the length of the shear span.
The resistance diagram can easily be modified to take advantage of any
end anchorage or slab reinforcement, and the loading diagram can be of
any shape.
A worked example using data from shear-bond tests is given in Section
3.4.3.
The only type of end anchorage for which design rules are given in
British or European codes is the headed stud, welded through the sheeting
to the top flange of a steel beam. The resistance of the anchorage is based
on local failure of the sheeting, as explained elsewhere [17].

µ R Ed , where µ

3.3.3 Resistance of composite slabs to vertical shear

Tests show that resistance to vertical shear is provided mainly by the
concrete ribs. For open profiles, their effective width b 0 should be taken as
the mean width, though the width at the centroidal axis (Fig. 3.2(a)) is
accurate enough. For re-entrant profiles, the minimum width should be
used.
This shear resistance is given by the method of EN 1992-1-1 for con-
crete beams. Reinforcement contributes to the resistance only where it is
fully anchored beyond the cross-section considered. The sheeting is un-
likely to satisfy this condition. The resistance of a composite slab with
ribs of effective width b 0 at spacing b is then

V Rd = ( b 0 / b ) d p v min per unit width (3.20)

where d p is the depth to the centroidal axis (Fig. 3.2(a)) and v min is the
shear strength of the concrete.