Civil Engineering Reference
In-Depth Information
the hook is governed by
d
b
. To determine the development lengths needed for standard
hooks, the ACI (12.5.2) requires the calculation of
0.02
f
y
d
b
dh
c
f
dh
, according to ACI Section 12.5.1, may not be less than 6 in. or 8
d
b
.
For deformed bars the ACI, Section 12.5.2, states that
The value of
in this expression can be taken
equal to 1.2 for epoxy-coated reinforcing and the
used equal to 1.3 for lightweight ag-
gregate concrete. For all other cases
and
are to be set equal to 1.0.
0.24
f
y
In SI units
dh
d
b
c
f
dh
is measured from the critical section of the bar to the out-
side end or edge of the hooks, as shown in Figure 7.13.
The modification factors that may have to be successively multiplied by
The development length
dh
are listed in
Section 12.5.3 of the Code and are summarized in subparagraphs (a) to (d). These values
apply only for cases where standard hooks are used. The effect of hooks with larger radii is
not covered by the Code. For the design of hooks, no distinction is made between top bars and
other bars. (It is difficult to distinguish top from bottom anyway when hooks are involved.)
(a)
Cover.
When hooks are made with #11 or smaller bars and have side cover val-
ues normal to the plane of the hooks no less than
2
2
in. and where the cover on
the bar extensions beyond 90
hooks are not less than 2 in., multiply by 0.7.
Figure 7.13
Hooked-bar
details for development of
standard hooks.
