Civil Engineering Reference
In-Depth Information
load
N
u
. Should a wall be subject to a tensile load
N
u
, the value of
V
c
may not be
larger than the value obtained with the following equation:
N
u
500
A
g
f
c
b
w
d
0
V
c
2
1
(ACI Equation 11-8)
6.
Using a more detailed analysis, the value of
V
c
is to be taken as the smaller
value obtained by substituting into the two equations that follow, in which
N
u
is the factored axial load normal to the cross section occurring simultaneously
with
V
u
.
N
u
is to be considered positive for compression and negative for ten-
sion (11.10.6).
c
hd
N
u
d
4
V
c
3.3
f
(ACI Equation 11-29)
w
or
c
0.2
N
u
/
w
h
)
M
u
V
u
c
w
(1.25
f
V
c
0.6
f
hd
(ACI Equation 11-30)
w
2
The first of these equations was developed to predict the inclined cracking
strength at any sec
ti
on through a shear wall corresponding to a principal tensile
stress of about at the centroid of the wall cross section. The second equati
on
was developed to correspond to an occurrence of a flexural tensile stress of
at a section
c
4
f
c
6
f
w
/2 above the section being investigated. Should
M
u
/
V
u
w
/2 be
negative, the second equation will have no significance and will not be used.
In SI units, these last three equations are as follows:
c
0.3
N
u
A
g
f
V
c
1
b
w
d
0
(ACI Equation 11-8)
6
c
hd
N
u
d
4
1
V
c
4
f
(ACI Equation 11-29)
w
f
c
2
N
u
c
w
w
h
1
2
hd
10
V
c
f
(ACI Equation 11-30)
M
u
V
u
w
2
7.
The values of
V
c
computed by the two preceding equations at a distance from the
base equal to
w
/2 or
h
w
/2 (whichever is less) are applicable for all sections be-
tween this section and one at the wall base (11.10.7).
8.
Should the factored shear
V
u
be less than
V
c
/2 computed as described in the
preceding two paragraphs, it will not be necessary to provide a minimum amount
