General Order 64-A
Section IV
Strength Requirements For All Classes Of Lines
49.1 Poles, Towers and Other Structures
A.
Strength
Wood poles shall be of sound
timber, free from defects which would materially reduce their strength or
durability and they shall have sufficient strength to withstand, with safety
factors at least equal to those specified in Rule 44, the maximum stresses to
which they are subjected under the loading assumptions set forth in Rule
43. Certain poles are subject to
special stresses due to angles in the line, dead-ending of conductors or other attachments,
which stresses must be included in computing the loading and safety
factor. Poles subject to these special
stresses sometimes require the use of guys, in which case the pole below the
point of guy attachment shall be considered merely as a strut, the guy taking
all the lateral stresses. In such cases
the pole strength requirement shall apply at the point of guy attachment rather
than at the ground line. Spliced wood
poles shall not be used in crossing or conflicts where Grade “A” or “B” construction
is required. The ultimate strength is
given in Rule 48.
Steel and reinforced concrete
poles, together with their foundations, shall be of such material and
dimensions as will withstand the loads with safety factors at least equal to
those specified in Rule 44. The
materials for these poles shall conform to the requirements of Rule 48.2 and
48.3. (For loadings and safety factors
see Rules 43 and 44.)
B.
Dimensions and Settings
The nominal top diameter of poles
shall not be less than the following:
Grade “A” heavy loading district – 7 inches minimum top diameter
Grade “A” light loading district – 6 inches minimum top diameter
Grades “B” and “C” heavy and light loading districts – 6 inches minimum top diameter
Grade “F” heavy and light loading districts carrying four open wires or less – 12 inches minimum perimeter; exceeding four open wires and for cable – 15 inches minimum perimeter.
Note – Poles having a ground line circumference of less than 12 inches are not safe to climb unless supported by guys, pike Poles, etc.
The character of soil to a large extent determines the depth of pole setting and the following depths considered applicable for good firm soil. Where the soil is not firm, special methods of pole setting must be resorted to. Where poles are set subject to heavy strain, or at corners and curves, a greater depth should be used. In rock the minimum depth shall be 3 feet.
For communication lines sawed of a cross-section of 36 square inches or less may be set to a depth of 6 inches less than the specifications shown in the following table:
Table 5 Pole Setting Depths |
|
Total length of pole feet |
Depth in ground feet |
20 |
4 |
25 |
4.5 |
30 |
5 |
35 |
5 |
40 |
5.5 |
45 |
6 |
50 |
6.5 |
55 |
7 |
60 |
7 |
65 |
7.5 |
70 |
7.5 |
75 |
8 |
80 |
8 |
C.
Gains
On round wood poles gains shall
be provided for cross arms. The maximum
depth shall not exceed on inch shall be of the same width at the cross arms. Approved mechanical gains are permitted.
D. Replacements: (See Rule 44.2.)