deleting the requirement for aerial buses and line
structures. Delete wire brackets if not required.
Maximum use will be made of "standard," "custom," or
"pre-fabricated" structure designs. Coordinate with
the local utility as well as with structure
manufacturers. Also, coordinate with SD-04, Detail
Drawings. Modify and/or delete subparagraphs as
required. Structures will be designed for not less
than 4.4 kN (1000 pounds) tension per conductor.
Normally, short slack spans from the utility system
should be provided to ensure that conductor tensions
are kept to a minimum.
Foundations will be designed based on available data
from soil borings and detailed on the project
drawings. Where soil-bearing pressures are not
known, foundations for a soil-bearing pressure of
not more than 191.5 kPa (4000 psf) should be
provided. The large overturning moments created by
the incoming aerial conductors will be considered in
the foundation design and a safety factor of not
less than 1.5 should be provided. The designer will
ensure that Section 03300A CAST-IN-PLACE STRUCTURAL
Concrete covers the class of concrete required for
foundations associated with a main electric supply
station, but concrete shall have not less than 17.2
MPa (2500 psi) compressive strength.
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Structures shall be provided as shown to support incoming line conductors,
switches, instrument transformers, air terminals and aerial buses. Steel
structural items shall conform to Section 05120 STRUCTURAL STEEL.
Structures, except for incoming primary lines, shall be of the low-profile
type. Structures shall utilize round or rectangular tubular steel
construction or equivalent H/I-beam support elements. Lattice type
supports are not acceptable. Structural steel and miscellaneous items
shall comply with ASTM A 36/A 36M, ASTM A 572/A 572M, ASTM A 575, ASTM A 576
or ASTM A 633/A 633M, or equivalent aluminum. General configurations are
indicated. Exact dimensions and arrangements may be varied, dependent upon
site limitations, to permit use of a manufacturer's standard equipment and
structures. Air terminals, [not less than 1.8 m 6 feet in length] [of the
length shown], shall be provided on each structure column for lightning
protection. [Static wire brackets for incoming overhead ground wires shall
be provided on each incoming dead-end line structure and elsewhere as
indicated.]
2.4.1.1
Pre-fabricated Structure Design
Structures shall be designed for a maximum tension of [4.5] [_____] kN
[1000] [_____] pounds per conductor. Overhead ground or static wires shall
be counted as conductors in determining strength requirements. Detail
drawings shall show markings of units for placement, location and sizes of
attachments, and complete data on fabrications.
2.4.1.2
Structure Finish
Aluminum structures shall have a uniform satin finish and shall not be
painted. Steel structures shall be hot-dip galvanized in accordance with
SECTION 16311A
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