TM
5-811-1/AFJMAN
32-1080
IN FORMULAS BELOW
USING VALUES BELOW
Dc = Conductor diameter (in)
D n = Conductor plus NESC additional ice thickness
requirement (in)
W = NESC wind pressure requirement (lb/ft2)
L = Length of pole spacing (ft)
N
= Number of conductors at same height above grade
Hc = Height of conductor above grade (ft)
Mc = Bending moment at base of pole from conductor
(ft-lb)
P t = Wind pressure on pole at the topa
Pg = Wind pressure on pole at the grounda
Ct = Circumference of pole at top (in)
Cg = Circumference of pole at grade (in)
Ht = H e i g h t o f t o p o f p o l e a b o v e g r a d e ( f t )
Mp = Bending moment at base of pole from wind on
pole (ft-lb)
Sm = S e c t i o n m o d u l u s a t b a s e o f p o l e ( i n 3 )
O f = Overload factor from NESC table 261-3
2
Fs = F i b e r s t r e s s i n p o l e ( l b / i n )
EXAMPLE FOR HEAVY LOADING DISTRICT
a
Lb per foot of circumferences
b Courtesy of
Keller & Gannon
Figure 6-11. An Example of a Pole Strength Analysis.
6-19
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