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Consulting Engineer SUBJECT:
12930 SW 133 Court, Miami, FL 33186 Calculations for picket fence pole embedment.
305-969-2776 FAX 305-969-3544 Mr. Camilo P. Ortega's home.
Wind Calculations (From ASCE 7-88)
Exposure C, importance factor I= 1.05 and basic wind speed of 110 mph.
This structure is considered as "other structures" and the wind forces are:
F=qZ Gh Cf Af for main system and F=qZ GZ Cf Af for components and cladding, where:
qZ=0.00256KZ(IV)2 and is evaluated at height z above ground, Gh and GZ are from table 8, Cf is from
table 14 and Af is the area in consideration.
Obtaining values for k from table 6 of the standard and for exposure C, have the following results:
Height above ground level kZ qZ(psf)
0-15 0.80 27.32
From table 8 Gh = 1.32. This fence has pickets 1 inch wide perpendicular to the wind directiiOn. These
pickets are at 5 inches on centers, therefore the ratio of solid area to gross area :s 115-or 0.20. From table
14, for flat-side members Cf= 1.8. The fence is 6 feet high so A f=0.5 SF.
With this set of values F = 32.46 lbs per each picket. The fence's posts are located every_ 5'40" so we
have 14 pickets per post. That is a force of 454.4 lbs at each post, located at 3' above ground.
Pole embedment
Preliminary calculation
For a presumptive soil capacity of 2,000 psf, the allowable value per foot of depth below natural grade
may be taken as 200 psf. The preliminary depth is given as:
d = 3V 12 hP
Bp
Where
d=depth of embedment, ft.
h=height above groundline at which force is applied, ft
P=applied horizontal load on pole, lb
B=butt diameter of pole or concrete casing, ft
p=allowable lateral soil pressure, psf.