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Introduction to Steel Utility Poles

Richard F. Aichinger, PE,
John C. Huang, Ph.D., PE,

Course Outline

This course introduces steel utility poles to engineers in the utility industry. It provides the detailed information on current design standards, load and strength factors, and the performance of the steel utility poles. This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of course materials.

Learning Objectives

At the conclusion of this course, the student will:

Course Content

steel utility poles Because of the material characteristics, steel utility poles are stronger, more durable, and environmentally friendlier than their wood counterparts. In addition to being recyclable, another one of the environmental advantages of steel distribution poles is that they are resistant to insects and rot. Therefore, unlike traditional wood poles, steel poles do not need toxic chemical preservative treatments and do not create future hazardous waste disposal concerns.

Steel utility poles are fabricated with uniform dimensions from ASTM tolerance materials - providing superior strength, consistent performance, and enhanced reliability. Steel poles also have the flexibility to be designed as direct wood pole replacements, or can be engineered to meet any specific loading criteria. To prevent corrosion, steel distribution poles can be galvanized or coated. They are lighter in weight and easier to install, require less maintenance, and offer lower overall life cycle cost.

When a steel pole is designed as direct wood pole replacement, two main factors govern the selection of a wood "equivalent" steel pole. They are the length of the poles and the groundline moment capacity. ANSI 05.1 "American National Standard for Wood Poles - Specifications and Dimensions" dictates the minimum moment capacity for each pole:

  1. The poles are embedded a minimum depth which is at least 10% x pole total length plus two feet;

  2. The moment is developed by a single horizontal force applied two feet from the top of the pole, resulting in the linear minimum moment capacity curve throughout the above ground portion of the pole.

The "Equivalent Steel Pole" loading is determined by multiplying the horizontal load required by ANSI 05.1 (for each wood pole class) by the ratio of National Electrical Safety Code (NESC) defined overload factors for wood and steel poles.

Wind loads normally have the greatest impact on the design of the utility poles. Other loads affecting the design of the utility poles include cable/wire self-weight and possible ice load.

Steel poles shall also be designed so their stresses meet ASCE Manual 72 "Design of Steel Transmission Pole Structures" allowables for bending and local buckling over the entire length of the pole (not just at the groundline).

The advantage of steel poles is structural designs meeting minimum stresses defined by ASTM Standards rather than mean stress values as used by wood. This assures that steel poles achieve the required equivalent load capacity every time, with consistent dimensions and predictable performance.

In this lesson, you need to

  1. View the slide show: Design & Testing of Steel Poles, which provides the detailed information on current design standards, load and strength factors, and the performance of the steel utility poles. This slide show (a Power Point presentation) can also be downloaded free of charge by clicking on the following hypertext: Download AISI steel utility poles online.ppt (3.2 MB).

  2. Study the Frequently Asked Questions regarding steel utility poles.

Once you finish viewing the slide shows and studying the FAQ, you need to take a quiz to obtain the PDH credits.

Take a Quiz


Additional Technical Resource and Further Readings:

The current National Electric Safety Code (NESC, 1997 edition) contains an apparent disprepancy in steel and wood pole safety factors. This disprepancy is expected to be corrected in the 2002 edition of NESC.

If you need a copy of 1997 National Electrical Safety Code or ASCE Manual 72 - Design of Steel Transmission Pole Structures (Second Edition, 1990), you may visit

For additional information on steel utility poles, please visit the websites of the following steel pole manufacturers:

Thomas & Betts Corporation

Valmont Industries, Inc.


Acknowledgment: acknowledges the sponsorship of American Iron and Steel Institute (AISI) for this online course.


Once you finish viewing the slide shows and studying the FAQ, you need to take a quiz to obtain the PDH credits.

DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered professional engineer. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.