Civil Engineering Reference
In-Depth Information
8.6
WEB REINFORCEMENT
When the factored shear
V
u
is high, it shows that large cracks are going to occur unless
some type of additional reinforcing is provided. This reinforcing usually takes the form of
stirrups that enclose the longitudinal reinforcing along the faces of the beam. The most
common stirrups are
shaped, but they can be
shaped or perhaps have only a single
vertical prong, as shown in Figure 8.3 a to c. Multiple stirrups such as the ones shown in
Figure 8.3(e) are considered to inhibit splitting in the plane of the longitudinal bars. As a
consequence, they are generally more desirable for wide beams than the ones shown in
Figure 8.3(d). Sometimes it is rather convenient to use lap-spliced stirrups such as the
ones shown in Figure 8.3(g). These stirrups, which are described in ACI Section 12.13.5,
Open stirrups for beams with neglible torsion (ACI 11.6.1)
hangers
(a)
(b)
(c)
(d)
(e)
Closed stirrups for beams with significant torsion (see ACI 11.6.2.1)
These types of
stirrups are not
satisfactory for
members designed
for seismic forces
Not less
than
1.3
d
(f)
(g)
Concrete confinement
both sides
Concrete confinement
one side
Concrete confinement
one side
(h)
(i)
(j)
Figure 8.3
Types of stirrups.
