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NESC Safety Rules for Overhead Lines
Overload Factors for Structures1, Crossarms, Guys, Foundations, and Anchors
| Overload Factors |
| |
Grade B |
Rule 250B Loads
Vertical Loads3 |
1.50 |
Transverse Loads
Wind
Wire Tension |
2.50
1.652 |
Longitudinal Loads
At Crossings
In General
At Deadends |
1.10
1.652 |
Elsewhere
In General
At Deadends |
1.00
1.652 |
| Rule 250C Loads |
1.00 |
| 1 |
Includes poles. |
| 2 |
For guys and anchors associated with structures supporting communication conductors and cables only, this factor may be reduced to 1.33. |
| 3 |
Where vertical loads significantly reduce the stress in a structure member a vertical overload factor of 1.0 should be used for the design of such member. Such member shall be designed for the worst case loading. |
Alternate Overload Factors for Wood and Reinforced (Not Prestressed)
Concrete Structures1,5
| Overload Factors |
| |
Grade B |
| |
When Installed |
At Replacement2,3 |
Rule 250B Loads
Vertical Loads4 |
2.20 |
1.50 |
Transverse Loads
Wind (at crossings)
Wind (elsewhere)
Wire Tension |
4.00
4.00
2.00 |
2.67
2.67
1.33 |
Longitudinal Loads
In General
At Deadends |
1.33
2.006 |
1.00
1.337 |
| Rule 250C Loads |
1.33 |
1.00 |
| 1 |
Includes poles. |
| 2 |
Where a wood structure is built for temporary service, the overload factors at replacement may be used provided the designated fiber stress is not exceeded during the life of the structure. Where a reinforced concrete (not prestressed) structure is built for temporary service, the overload factors at replacement maqy be used. |
| 3 |
When structure strength deteriorates to the level of the loads multiplied by the overload factors required at replacement, the structure shall be replaced or rehabilitated. If a structure is replaced, it shall meet the "when installed" overload factors at replacement. Rehabilitated portions of structures shall have overload factors at the time of rehabilitation greater than of those required "at replacement". |
| 4 |
Where vertical loads significantly reduce the stress in a structural member, a vertical overload factor of 1.0 should be used for the design of such member. Such members shall be designed for the worst-case loading. |
| 5 |
Metal portions of a structure may be designed using the overload factors in Tables 2531. |
| 6 |
For unguyed wood poles supporting communication conductors and cables only, this factor may be reuced to 1.33. |
| 7 |
For unguyed wood poles supporting communication conductors and cables only, this factor may be reuced to 1.0. |
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