Civil Engineering Reference
In-Depth Information
Foundation at the left pier: Assume that the footing extending across the opening
yields 6″ to the right of the wall pier so that the determination of the soil bearing pressure
can be simplified by using a rigid foundation analysis. Determine if this length of
footing can maintain overturning stability for the pier and keep the soil pressures within
allowable values. Check load combination
D
+
W
:
L
ftg
=+ +=
05 13305233
.
.
.
.
ft
wt conc
.
. = 150
pcfreinforced
w
DL
= 0 345
.
klfdeadloadoffdn includings
.
oilwtand turndown
.
Pt
=
L
wt
=
067133 0150178
.
(.
(. )
=
.
kdeadloadoffdn wall
.
DL
wall
pier
conc
∑
M
right
=
0
M
o
= 206
.
ft-k
133
2
.
0 345 233
2
.
( .
)
2
M
R
=
0152
.
()(.
+
0 178
+
194233
.
).
−
05
.
−
+
=
369
.
ft-k
M
M
369
206
.
.
R
FS
..
=
=
=
17915
.
>
.
OK
O/T
o
or
0.6
M
R
=
2 214
.
ft-k > 2.06
∴
OK
∑
M
left
=
0
(.
0 178
+
194117
.
(. )
−
0152
.
()
+
2060345 2333117
.
+
.
(.
)( .
)
x
=
=
1 772
.
ft
292
.
233
2
.
L
e
=
1 772
.
−
=
0 607
.
ft
> =
0 388
.
ft
6
Therefore the resultant is outside the kern.
m
=
2331772
.
−
.
=
0 558
.
ft
2
3
P
2292
3133 0 558
(. )
(. )( .
SBP
=
=
=
2 623
.
ksf
bm
)
If the allowable soil bearing pressure is greater than 3.325 ksf, then an additional
length of footing on each side of the stem wall can be added to reduce the soil bearing
pressure or to increase stability. However, the extended footing must be checked for
strength under the new loading condition.
Foundation at the right pier (see Fig. 13.12):
The moment at the base of the right pier is more
than 3 times greater than the moment at the left pier. By inspection, a significant length
of footing on the left side of the pier will be required to pick up enough dead load to
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