Civil Engineering Reference
In-Depth Information
transverse compression, which enhances the shear resistance in the region
CJ by an amount at least equivalent to the contribution the reinforcement
would make, in the absence of transverse bending.
3.6.3.1
Design rules for transverse reinforcement in solid slabs
For this subject, EN 1994-1-1 refers to EN 1992-1-1 for concrete struc-
tures. Its rules for transverse reinforcement are based on a truss analogy
in which the slope of the diagonal members,
θ
f
, may be chosen, within
defined limits, by the designer. In this explanation, the long-established
angle of 45° is used.
Part of a composite beam is shown in plan in Fig. 3.22. The truss model
for transverse reinforcement is illustrated by triangle ACE, in which CE
represents the reinforcement for a unit length of the beam, of area
A
e
, and
v
L
is the design shear flow for a cross-section of type B-B (Fig. 3.20)
above the edge of the steel flange (shown by a dashed line). The shear
flow for the connectors, 2
v
L
, is applied at point A, and is transferred by
concrete struts AC and AE, at 45°
to the axis of the beam.
The strut force is balanced at C by compression in the slab and tension
in the reinforcement. The model fails when the reinforcement yields. The
tensile force in it is equal to the shear on a plane such as B-B caused
by the force
v
L
. The design equation gives the minimum area
A
e
of
reinforcement:
v
L,Ed
<
v
L,Rd
=
A
e
f
sd
(3.75)
Another requirement is that concrete struts such as AC do not fail in
compression. Their design compressive stress is given in EN 1992-1-1 as
0.6(1
−
f
ck
/250)
f
cd
(3.76)
Figure 3.22
Truss model for transverse reinforcement
