Civil Engineering Reference
In-Depth Information
Figure 14.34
Assume
K
tr
0
f
y
c
d
d
b
3
40
K
tr
d
b
c
f
(1.0)(1.0)(1.0)(1.0)
2.564
0
1.128
60,000
3000
3
40
36.14 diameters
d
(36.14)(1.128)
41
M
n
Maximum permissible
d
V
u
a
2644.8
65
(1.3)
7
59.90
41
OK
Note:
If this condition has not been satisfied, the permissible value of
d
could have been in-
creased by using smaller bars or by increasing the end anchorage
a
, as by the use of hooks.
Negative-Moment Reinforcement
Section 12.12 of the Code says that the tension reinforcement required by negative mo-
ments must be properly anchored into or through the supporting member. Section 12.12.1
of the Code says that the tension in these negative bars shall be developed on each side of
the section in question by embedment length, hooks, or mechanical anchorage. Hooks
may be used because these are tension bars.
Section 12.10.3 of the Code says that the reinforcement must extend beyond the
point where it is no longer required for moment by a distance equal to the effective depth
of the member or 12 bar diameters, whichever is greater, except at the supports of simple
beams or at the free ends of cantilevers. Section 12.12.3 of the Code says that at least
one-third of the total reinforcement provided for negative moment at the support must
