Civil Engineering Reference
In-Depth Information
Figure 13.23
Righting moment
Force
Moment arm
Moment
W
1
(1.5)(11.5)(150)
2588 lb
5.75
14,881 ft-lb
W
2
731 lb
4.08
2982 ft-lb
W
3
2925 lb
4.75
13,894 ft-lb
W
4
(22.5)(6.25)(100)
14,062 lb
8.37
117,699 ft-lb
*
R
v
20,306 lb
(
2
)(19.5)(
12
)(150)
(19.5)(
1
12
)(150)
M
149,456 ft-lb
*Includes surcharge.
Safety factor against overturning
149,456
70,560
2.12
2.00
OK
Factor of Safety Against Sliding
Here the passive pressure against the wall is neglected. Normally, it is felt that the factor of safety
should be at least 1.5. If it is not satisfactory, a little wider footing on the heel side will easily take
care of the situation. In addition to or instead of this solution a key, perhaps 1 ft-6 in.
1 ft-6 in.
(size selected to provide sufficient development length for the dowels selected later in this design)
can be used. Space is not taken here to improve this safety factor.
