Civil Engineering Reference
In-Depth Information
Using 0.00333,
A
x
(0.00333)(12)(20.5)
0.82 in.
2
/ft
Use #8 @ 11
d
required calculated with ACI Equation 12-1 for #8 top bars with
c
2.50 in. and
K
tr
0 is 43 in.
72 in. available.
Heel reinforcing is shown in Figure 13.25.
Note:
Temperature and shrinkage steel is normally considered unnecessary in the heel and toe.
However, the author has placed #4 bars at 18 in. on center in the long direction, as shown in Figures
13.25 and 13.27, to serve as spacers for the flexural steel and to form mats out of the reinforcing.
OK
Design of Toe
For service loads, the soil pressures previously determined are multiplied by a load factor of 1.6 be-
cause they are primarily caused by the lateral forces, as shown in Figure 13.26.
V
u
10,440
7086
17,526 lb
(The shear can be calculated a distance
d
from the face of the stem because the reaction in
the direction of the shear does introduce compression into the toe of the slab, but this advantage
is neglected because 17,526 lb is already less than the 19,125 lb shear in the heel, which was
satisfactory.)
3.75
3
2
3
M
u
at face of stem
(7086)
(10,440)
3.75
34,958 ft- lb
M
u
(12)(34,958)
(0.9)(12)(20.5)
2
92
bd
2
less than
min
Figure 13.25
Heel reinforcing.
Figure 13.26
