Civil Engineering Reference
In-Depth Information
dh
=
26
"
Point of
tangency
Critical section
1
2
12
d
b
=
13
"
Figure 7.17
(c)
Using 90
hooks (see Figure 7.17)
dh
26
as side cover
2
2
7.6
DEVELOPMENT LENGTHS FOR WELDED WIRE FABRIC
IN TENSION
Section 12.7 of the ACI Code provides minimum required development lengths for de-
formed welded wire fabric, whereas Section 12.8 provides minimum values for plain
welded wire fabric.
The minimum required development length for deformed welded wire fabric in ten-
sion measured from the critical section equals the value determined for
d
as per ACI Sec-
tion 12.2.2 or 12.2.3 multiplied by a wire fabric factor from ACI Section 12.7.2 or 12.7.3.
This factor, which follows, contains the term
s
w
, which is the spacing of the wire to
be developed. The resulting development length may not be less than 8 in. except in the
computation of lap splices. You might note that epoxy coatings seem to have little effect
on the lengths needed for welded wire fabric, and it is thus permissible to use
1.0.
The wire fabric factor for welded wire fabric with at least one crosswire within the
development length not less than 2 inches from the critical section is
f
y
35,000
f
y
not less than
5
d
b
s
w
but need not be taken
1.0.
In SI units for welded wire fabric with at least one crosswire within the develop-
ment length and not less than 50 mm from the point of the critical section, the wire fab-
ric factor is
f
y
240
f
y
5
d
b
s
w
not less than
, but need not be taken
1.0.
The yield strength of welded plain wire fabric is considered to be adequately devel-
oped by two crosswires if the closer one is not less than 2 in. from the critical section. The
Code (Section 12.8), however, says that the development length measured from the criti-
cal section to the outermost crosswire may not be less than the value computed from the
following equation, in which
A
w
is the area of the individual wire to be developed.
0.27
A
w
f
y
but not
6 in.
s
w
c
f
