Code of Massachusetts Regulations › 220 CMR - DEPARTMENT OF PUBLIC UTILITIES › Title 220 CMR 125.00 - Installation And Maintenance Of Electric Transmission Lines › Section 125.25 - Strength Requirements

Current through Register 1525, July 5, 2024
(1)
General
. Structures shall be capable of supporting,
		without failure or permanent set in any part, the loads specified in
		220 CMR 125.24
		multiplied by the following overload factors:
Table 1
Type of Supporting
				  Structure
Vertical
Loads
Wind
Loads
Conductor
Tension
Metal Reinforced Concrete, Sawn Timber, Laminated
				  Wood, Guys
1.27**
2.54
1.65
Wood Pole-When Installed
4.00*
4.00*
2.00*
Wood Pole-At Replacement
2.67
2.67
1.33
* When lines are built for a fixed period of temporary service
		  not exceeding five years, the prescribed overload factors at installation may
		  be decreased, provided that at no time during the life of the line will the
		  overload factors be less than those required at replacement.
** When vertical loading contributes all or a major portion of
		  the stress in a member, the overload factor shall be increased from 1.27 to
		  2.00.
For metal reinforced concrete, sawn timber or laminated wood
		  members of structures and for guys, stresses resulting from loads specified in
		  220 CMR 125.64 multiplied by the appropriate overload factors specified above
		  shall not exceed the yield or ultimate stresses, as applicable, of the
		  particular materials.
For wood poles, including spar crossarms, bending stresses
		  resulting from loads specified in
		  220 CMR 125.24
		  multiplied by the appropriate overload factors specified above shall not exceed
		  the ultimate fiber stresses approved as standard by the American National
		  Standards Institute under conditions specified in Section 4 of ANSI 05.1-1963,
		  or latest revision thereof
All parts of structures upon which personnel can stand or climb
		  shall be capable of supporting such weight.
(2)
Corrosion
		Resistance
. All metal parts of supporting structures, guys, anchor
		rods, conductors, insulators, and hardware shall be corrosion-resistant
		materials or shall be protected by galvanizing, painting, or other treatment
		which will effectively retard corrosion. Such protective covering shall be
		adequately maintained.
(3)
Metal Supporting Structures.
(a)
Thickness of
		Metal
. The thickness of metal in members of metal supporting
		structures shall be not less than the following:
Table 2
Thickness of Main Members of Cross-
Arms and
				Legs, In.
Thickness of Other Members,
Inches
For localities where experience has shown rapid
				corrosion
1/4
3/16
For other localities
3/16
1/8
(b)
Slenderness Ratio of Compression Members
. The
		slenderness ratio, L/R, of a compression member shall not exceed the following
		(these figures do not apply to the completed structure):
Table 3
Kind of Compression Member
L/R
Leg members
150
Other members having figured stresses
200
Secondary members without figured stresses
250
(c)
General Construction Features
. Metal supporting
		structures, including parts of footings above ground, shall be constructed so
		that all exposed parts are accessible for inspection, cleaning, and painting,
		and so that pockets are not formed in which water can collect.