ASCE/SEI 48-19
Design of Steel Transmission Pole Structures. A uniform basis for design, detailing, fabrication, testing, assembly and erection of tubular steel poles on caissons, steel piling or direct embedment. It replaced ASCE/SEI 48-11.
All guides
Guide
Metal utility poles: a buyer’s guide to steel poles
Steel utility poles are metal utility poles made as hollow, tapered steel tubes, round or multi-sided. They are protected by hot-dip galvanizing (ASTM A123), paint, weathering steel or a mix of these. Steel resists rot, insects and fire better than wood, and buyers can order steel poles as wood-class equivalents, matched to the strength of an ANSI O5.1 wood pole class.
What a steel utility pole is
An engineered tube, built to a drawing.
A steel utility pole is a hollow tube, round or multi-sided (polygonal), that tapers from a wide butt to a narrow top. Long poles can ship in pieces joined by a slip joint, where one tapered section telescopes over the next, or by bolted flanges.
Because the pole is made to a drawing, its dimensions and strength repeat from pole to pole. The USDA Rural Utilities Service (RUS) guide specification, Bulletin 1724E-214, asks bidders to state each pole’s diameters, taper, wall thickness, steel grade, weight and tip load, and sets a minimum plate thickness of 3/16 inch.
Galvanizing, weathering steel and coatings
The finish decides how long the steel lasts, above all at the groundline.
RUS accepts four finishes: hot-dip galvanizing, zinc primer with paint, weathering steel, and a below-grade coating on the buried section.
- Hot-dip galvanizing. The steel is dipped in molten zinc, which bonds to its surface. ASTM A123/A123M, revised in 2024, sets coating thickness, finish, appearance and adherence. Bolts are galvanized under ASTM A153.
- Weathering steel. Steel to ASTM A588 or A871 forms its own protective oxide layer. RUS says A588 poles should not be galvanized (the steel is high in silicon), and weathering steel poles must be designed without water traps.
- Paint. RUS describes a zinc primer with two finish coats. Snohomish County PUD’s wood-equivalent pole standard requires painting after galvanizing.
- Groundline protection. RUS calls for at least 16 mils of polyurethane on the embedded section and, where the owner asks, a steel ground collar at the groundline. The Tennessee Valley Authority (TVA) adds a ground sleeve to its embedded steel poles because that is where corrosion most threatens pole life.
Wood-equivalent classes
How a steel pole is matched to an ANSI O5.1 wood class, and why the method must be written down.
Wood poles are graded by class under ANSI O5.1. Each class is defined by a horizontal load applied 2 feet from the top: 4,500 pounds for Class 1 down to 1,900 pounds for Class 5. Because many line designs use these classes, buyers often ask for “wood-equivalent” steel poles.
RUS shows why this needs care. Under the National Electrical Safety Code (NESC), wood carries a strength factor of 0.65 for Grade B district loading and steel carries 1.00. To match Class 1 on that basis, multiply 4,500 pounds by 0.65 and pick a steel pole rated for at least 2,925 pounds: RUS class S-02.9. Matching ultimate strength instead gives S-04.9.
| Wood class | ANSI O5.1 load, 2 ft from top | RUS steel class, Grade B district (0.65) | RUS steel class, equal ultimate strength (1.0) |
|---|---|---|---|
| Class 1 | 4,500 lb | S-02.9 (2,925 lb) | S-04.9 (4,875 lb) |
| Class 2 | 3,700 lb | S-02.4 (2,405 lb) | S-04.2 (4,160 lb) |
| Class 3 | 3,000 lb | S-02.0 (1,950 lb) | S-03.5 (3,510 lb) |
| Class 4 | 2,400 lb | Not in RUS tables | Not in RUS tables |
| Class 5 | 1,900 lb | Not in RUS tables | Not in RUS tables |
The RUS bulletin covers transmission poles, and its smallest class is S-02.0, so distribution utilities set their own rules (Snohomish County PUD applies the 0.65 factor). RUS warns that steel and wood never match at every point along the pole. The owner, not the manufacturer, should settle the equivalence and state it in the request for quote.
Design standards for steel poles
RUS Bulletin 1724E-214
Guide Specification for Standard Class Steel Transmission Poles (2019). A model purchase spec for unguyed, direct-embedded single poles designed to ASCE 48. Guyed poles and H-frames go to Bulletin 1724E-204.
ASTM A123/A123M
Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products. The reference RUS names for galvanized poles; threaded hardware falls under ASTM A153.
Buying by class does not replace engineering: RUS states that a complete structural analysis is still required for every structure.
Where steel makes sense
Storm hardening
The US Department of Energy (DOE) says non-wood poles can withstand higher wind speeds than wood, and that utilities replacing wood on transmission lines usually choose steel.
Wildfire areas
San Diego Gas & Electric reports replacing more than 34,000 wood poles with fire-resistant steel poles. TVA notes that steel poles are more fire-resistant than wood.
Woodpeckers, insects and rot
DOE notes that non-wood poles resist decay, insects and wildlife damage better than wood and avoid wood preservatives.
Consistent strength
NESC factors for wood allow for natural variability and decay over the pole’s life, which is why wood’s strength factor is lower.
Steel is not the answer everywhere. DOE notes that non-wood poles can be harder to repair, and in corrosive soils the groundline finish decides pole life.
Steel vs wood utility poles
General differences, from public guidance. Your engineer’s design governs.
| Factor | Galvanized steel | Treated wood |
|---|---|---|
| How it is made | Fabricated tube, uniform taper, steel grade on the drawing | Natural timber graded to ANSI O5.1 |
| Strength rating | RUS standard classes or a wood-equivalent spec | ANSI O5.1 classes (Class 1 to 5, H classes) |
| NESC strength factor, Grade B district | 1.00 | 0.65 |
| Weight | Lighter than wood (DOE) | Heavier; varies by species and class |
| Preservative | None needed | Required (for example CCA or creosote) |
| Rot, insects, woodpeckers | Resists decay and wildlife damage | Subject to decay and woodpecker damage |
| Fire | More fire-resistant than wood | Combustible |
| Main long-term concern | Corrosion at the groundline | Decay at the groundline |
| Estimated average service life (DOE) | About 80 years | 30 to 50 years, with wide variation |
Handling and installation
Two ways to set a steel pole: bury it, or bolt it to a foundation.
Direct embedment
RUS standard class poles are set in the ground like wood. RUS puts the point of fixity (where the pole acts as if clamped) at 7 percent of pole length above the butt and leaves embedment depth to the owner’s engineer. One steel distribution pole training course gives a minimum of 10 percent of length plus 2 feet.
Anchor-bolt base plates
The alternative is a welded base plate bolted to anchor bolts cast into a concrete foundation, such as a drilled pier. The Grand River Dam Authority’s specification, for example, has the anchor bolts ship as a rigid cage held by top and bottom plates.
Handling and framing
RUS requires poles to be designed for one-point (tilting) and two-point horizontal pickups. Field welding is not normally permitted, so put framing holes, steps, grounding pads and attachments on the shop drawings.
Lifecycle and recyclability
DOE cites an estimated average service life of about 80 years for steel poles, against 30 to 50 years for wood, with wide variation in practice. Keep coatings and ground collars on the inspection checklist. At end of service, the American Galvanizers Association states that steel and zinc can both be recycled without losing their properties, and an Oak Ridge National Laboratory (ORNL) review calls steel poles 100 percent recyclable.
Buying steel poles on Sourcewell Contract #060326-BIDR
A competitively solicited cooperative contract, free for eligible public agencies to use.
BIDR Technologies holds Sourcewell Contract #060326-BIDR, “Utility Poles with Related Equipment, Supplies, and Services,” through August 5, 2030. Sourcewell’s utility pole solicitation (#11229) lists one awarded contract: BIDR’s. The catalog includes galvanized steel poles from 25 to 70 feet in 5-foot steps, Classes 1 to 5, plus steel crossarms, anchors and guy wire, with delivery, installation and pole loading analysis available. See the utility pole contract page.
To buy, register your agency with Sourcewell (free for government and education entities), request a quote, then finalize with the contract number and your agency’s Sourcewell account number. The cooperative contracts guide explains the process; the pole materials and wood pole guides compare options.
What to put in a steel pole quote request
- Length, class and, for wood classes, the equivalence method
- Finish, below-grade coating and ground collar
- Direct embedment depth, or base plate with anchor bolts
- Framing holes, steps and grounding pad
- Quantity, delivery address and need-by date
You get a written quote at contract pricing with a delivery timeline. Request steel pole pricing.
Questions buyers ask
Are metal utility poles and steel utility poles the same thing?
Not always. “Metal” also covers ductile iron and aluminum poles, which some distribution utilities use. When utilities replace wood on transmission lines, DOE notes they usually choose steel. Galvanized steel is the metal option in the BIDR Technologies catalog under Sourcewell Contract #060326-BIDR.
Can a steel pole replace a wood pole of the same class?
Yes, if it is specified as a wood equivalent and the method is written down. RUS Bulletin 1724E-214 multiplies the ANSI O5.1 wood load by the ratio of strength factors, such as 0.65 for NESC Grade B district loading, then selects the steel class that meets it. Your engineer should still check deflection and actual loads.
How long do galvanized steel utility poles last?
DOE’s Grid Deployment Office cites an estimated average service life of about 80 years for steel poles, compared with 30 to 50 years for wood. Actual life depends mostly on the groundline, so below-grade coatings, ground collars and periodic inspection matter.
Can our agency buy steel poles without running its own bid?
Sourcewell competitively solicits its contracts, and eligible public agencies can use Sourcewell Contract #060326-BIDR at no cost and with no obligation to buy. Whether that meets your own procurement rules is your agency’s decision; Sourcewell states that each agency is responsible for its own due diligence and compliance.
Get contract pricing on steel poles
Send lengths, classes, finish and delivery site for a written quote at Sourcewell contract pricing. Call 321-576-3147 or email [email protected].
Sources
- Bulletin 1724E-214, Guide Specification for Standard Class Steel Transmission Poles (2019), USDA Rural Utilities Service
- New Guidance on Electrical Transmission Poles Offered in Updated ASCE Standard 48 (ASCE/SEI 48-19), Informed Infrastructure
- ASTM A123/A123M Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products, American Galvanizers Association
- 2024 HDG Specification Updates, American Galvanizers Association
- Guide for the Design of Prestressed Concrete Poles (1997), Joint ASCE Task Force and PCI Committee on Prestressed Concrete Poles, PCI Journal
- Material Standard 5000170.1, Wood Class Equivalent Ductile Iron and Steel Utility Poles, Snohomish County PUD
- Steel Pole Specifications (2025), Grand River Dam Authority
- Utility Pole Maintenance and Upgrades, Resilience Investment Guide (2024), US Department of Energy, Grid Deployment Office
- Assessment of Commercial Composite Power Pole Performance, ORNL/TM-2021/2068 (2021), Oak Ridge National Laboratory
- How TVA Weathers Storms (2018), T&D World
- Electric System Hardening, San Diego Gas & Electric
- Take a Second Look at Steel: Hot-Dip Galvanized Steel Sustainable Solution for Distribution Poles (2015), American Galvanizers Association
- Introduction to Steel Utility Poles, course S114, PDHonline
- Solicitation #11229, Utility Poles, Sourcewell
- How cooperative purchasing works, Sourcewell