Civil Engineering Reference
In-Depth Information
Figure 2.12
Haunch with connectors too close to a free surface
Figure 2.13
Detailing rules for haunches
ratio (the stiffness) in the elastic range exceeds the push-test value, but the
ultimate strength is about the same. For slabs in tension (e.g., in a region
of hogging moment), the connection is significantly less stiff [25] but the
ultimate shear resistance is only slightly lower. The reduction in stiffness
is one reason why partial shear connection (Section 3.6) is allowed in
Eurocode 4 only in regions of sagging bending moment.
There are two situations in which the resistance of a connector found
from push tests may be too high for use in design. One is repeated load-
ing, such as that due to the passage of traffic over a bridge. The other is
where the lateral restraint to the concrete in contact with the connector is
less than that provided in a push test, as in a haunched beam with con-
nectors too close to a free surface (Fig. 2.12). For this reason, the use of
the standard equations for resistance of connectors is allowed in haunched
beams only where the cross-section of the haunch satisfies certain con-
ditions. In EN 1994-1-1 these are that the concrete cover to the side of
the connectors may not be less than 50 mm (line AB in Fig. 2.13), and
that the free concrete surface may not lie within the line CD, which runs
from the base of the connector at an angle of 45° with the steel flange. A
haunch that just satisfies these rules is shown as EFG.
There are also rules for the detailing of reinforcement for haunches,
which apply also at the free edge of an L-beam.
Tests show that the ability of lightweight-aggregate concrete to resist
the high local stresses at shear connectors is slightly less than that of
