You are an engineer working for a utility company. Your project team is designing the power distribution (overhead wires) in a new subdivision. Shown in the following is the last pole along one of the streets. For this dead end configuration you have the following specifications:
Electric Pole:
Class 2, 100 feet long, with 10 feet buried in earth. Maximum axial load given in column load table.
Stub Pole:
Class 2, 50 feet long, with 10 feet is buried in earth. Maximum axial load given in column load table.
Anchor:
14” PISA with a maximum permitted pull-out load of 17,500 pounds.
Guys:
11k guys that have a maximum permitted tension load of 11,300 pounds.
Wires:
Three primary wires (A, B, and C) – 123.33 AAAC. Each is subject to 2140 pound tension (hence the name ‘high tension wire’).
Neutral - #3 Copper. subject to 1180 pounds tension
Finally, you have been instructed to use Class C construction standards. This means a safety factor of 1.1 must be used in your analysis.
The electric pole and the stub pole are at the edges of the roadway right-of-way. The anchor will be outside of the right-of-way and will require the subdivision to purchase land from the neighbouring farmer (who is VERY UNHAPPY about the subdivision in the first place.) Thus, your project leader, knowing that you are an expert in statics, has assigned you the task of determining the minimum guy lead length (to the nearest foot) for this pole configuration.
TABLE OF COLUMN LOADING LIMITS
50 FOOT UTILITY POLE
(Values based on distance from the top of the pole)
DISTANCE (ft.) MAXIMUM LOAD (lbs.)
1.0 12,600
1.5 13,325
2.0 14,050
2.5 14,775
3.0 15,500
3.5 16,150
4.0 16,800
4.5 17,450
5.0 18,100
5.5 19,175
6.0 20,250
6.5 21,325
7.0 22,400
7.5 23,750
8.0 25,100
8.5 26,450
9.0 27,800
9.5 29,225
10.0 30,650
10.5 32,075
11.0 33,500
11.5 35,625
12.0 37,750
12.5 39,875
13.0 42,000
13.5 44,125
14.0 46,250
14.5 48,375
15.0 50,500
15.5 53,975
16.0 57,450