Steel Utility Poles

1
American Iron and Steel Institutes Technical
Session
Steel Distribution Poles - The Material of the
Future
Design Testing of Steel Poles
- presented by - Richard F. Aichinger,
PE Manager of Engineering, Utility
Products Valmont Industries, Inc.
2
Designing For Equivalency

• Equivalency to what?
• Expected Strength
• Expected Life
• Expected Performance
• Deflection
• Handling
• Field Use

3
Designing For Equivalency

• Most pole used to date have been wood
• How do you design a Steel wood pole?
• You cant but you dont want to
• Instead you design a pole that meets minimum
  strength and performance requirements every time

4
Designing For Equivalency

• How do you design a Steel Distribution Pole?
• ANSI Standards
• ANSI 05.1
• National Electric Safety Code (ANSI C-2)
• ASCE Manual 72
• Material Manufacturing Proven Reliability
• Testing and Proven Product Experience

5
ANSI 05.1

• Provides performance and quality criteria for
  wood poles of various species
• Provides strength requirements which define the
  various pole Class definition (Class 6 to H-6)
• Defined by a Capacity Loading to be applied 2
  feet from the pole top
• Provides direct embedment depth

6
National Electrical Safety Code (ANSI C-2)

• A Safety Code
• By default, also a Design Code
• Provides for Design considerations for various
  line conditions (ice, wind ice, wind)
• Provides for Construction Grades to differentiate
  the allowable risk accepted in the design

7
National Electrical Safety Code (ANSI C-2)

• A Little History
• Provided for loading and strength since the early
  1900s to present
• Early editions were based on ultimate strength of
  materials
• Steel was first to be changed to Load Factor in
  1941

8
National Electrical Safety Code (ANSI C-2)

• 1941 Summary
• Material Grade B Grade C
• Steel 2.54 2.2
• wood 25 37.5
• (equiv. OLF) (4.0) (2.67)

9
National Electrical Safety Code (ANSI C-2)

• 1973 Wood was modified
• Material Grade B Grade C
• Steel 2.54 2.2
• wood 25 50
• (equiv. OLF) (4.0) (2.0)
• Familiar?
• wood is now lower than steel in Grade C.
• 1997 Edition introduced Strength Factors

10
National Electrical Safety Code (ANSI C-2)

• 1997 Edition Grade B
• Strength Factor Equiv.
  O.L.F.
• Load Type Overload Steel Wood
  Steel Wood Ratio
• Vertical 1.5 1.0 0.65
  1.5 2.31 0.65
• Transverse
• Wind 2.5 1.0
  0.65 2.5 3.85 0.65
• Tension 1.65 1.0
  0.65 1.65 2.54 0.65

11
National Electrical Safety Code (ANSI C-2)

• 1997 Edition Grade C
• Strength Factor Equiv.
  O.L.F. Ratio
• Load Type Overload Steel Wood
  Steel Wood
• Vertical 1.5 1.0
  0.85 1.5 1.76 0.85
• Transverse
• Wind 2.2 (steel) 1.0
  0.85 2.2 2.06 1.07
• 1.75(wood)
• Tension 1.1 (steel) 1.0
  0.85 1.1 1.53 0.72
• 1.3 (wood)

12
ASCE Manual 72

• The Steel Pole Design Guide
• Provides for the best practices of the industry
• Provides for the Design Requirements equated to
• AISC
• ACI
• AWS

13
Designing For Equivalency

• Equivalent Wood Pole Loading (B)
• ANSI Load x 2.5/4.0
• ANSI 05.1 Working Equivalent
• Pole Class Loading Load Steel Load
• 2 3700 925 2313
• 3 3000 750 1875
• 4 2400 600 1500
• 5 1900 475 1188

14
Designing For Equivalency

• CLASS 4 Pole has ANSI rated capacity of 2400.
• GRADE B CONSTRUCTION
• WOOD O.L.F. 4.0
• STEEL O.L.F. 2.5
• STEEL RATED LOAD BECOMES 2400 x 2.5/4.0
  1500
• GRADE C CONSTRUCTION
• WOOD O.L.F. 2.0
• STEEL O.L.F. 2.2
• STEEL RATED LOAD BECOMES 2400 x 2.2/2.0
  2640

15
Designing For Equivalency

• CLASS 4 Pole has ANSI rated capacity of 2400.
• GRADE B CONSTRUCTION
• WOOD O.L.F. 4.0
• STEEL O.L.F. 2.5
• STEEL RATED LOAD BECOMES 2400 x 2.5/4.0
  1500
• GRADE C (Expected NESC Change for 2002)
• WOOD O.L.F. 2.06
• STEEL O.L.F. 1.75
• STEEL RATED LOAD BECOMES 2400 x
  1.75/2.06 2039 (vs. 2640)

16
Designing For Equivalency

• Steel Allows for Designs that Consistently meet
  strength requirements by varying diameter and
  thickness
• ASCE Manual 72 provides criteria for Local
  Buckling of Tubular Steel
• Proven through years of use in other products
• Verified by EPRI and manufacturer testing
• Provides a pole that is consistent by design

17
Designing For Life

• Steel Allows for the Design of a Product that can
  be protected against deterioration
• Galvanizing provides a proven inside/out
  protection for most environments
• An additional groundline barrier coating provides
  extra protection at the most corrosive location
• When damaged by overload conditions, Steel will
  tend to locally yield rather than break or
  collapse, often times allowing the line to
  remain in service

18
Designing For Performance

• Deflection of steel poles are normally less than
  the equivalent wood pole based on the pole size
  defined by ANSI 05.1
• The following graph shows a representative
  comparison indicating the deflection of a Steel
  versus wood poles

19
Load Deflection of Steel vs. Wood Poles (40
Class 4, NESC Grade B)
20
Designing For Performance

• Weight of steel poles are normally much less than
  the equivalent wood pole providing added
  savings for field handling and maneuvering
• The following chart is a representative
  comparison of the weight of wood poles versus
  Steel Poles

21
Weight Comparison of Wood to Steel
22
Designing For Performance

• Additionally, Steel can be Designed for true
  design applications wood is seldom correctly
  considered for
• Guyed angles and corners
• NESC requirements
• Unguyed angles and corners
• Steel provides the necessary strength and
  flexibility of size and application

23
Designing For Reliability

• Steel Poles have been successfully used
• for over 30 years for the Electric Utility
  industry
• for over 40 years with the same product in other
  industries (lighting and traffic)
• Fabrication and Quality systems have evolved to
  keep up with customer demand, technology, and
  increasing Design sophistication

24
Designing Proven by Testing

• Steel Poles have been tested for as long as Steel
  Poles have been fabricated. But there is a
  difference
• Steel Poles are tested to Verify Design strength
  is attained as a Minimum
• wood poles are tested to determine the mean
  rupture strength

25
Designing Proven by Testing

• Steel Distribution Poles have been tested by
  independent firms (EDM in Fort Collins) and by
  the manufacturers using controlled conditions and
  sophisticated systems.
• Strength / Buckling tests to verify design
  acceptance for conditions including
• full tube sections
• tube sections with many cut holes to verify that
  condition
• attachment and guy hardware loading
• All showing the Strength and Reliability of Steel

26
Post Insulator Test On Steel Pole
27
Guy Attachment Test On Steel Pole
28
EPRI Test On 70 Class 2 Steel Pole
29
Testing at EPRI (Class 2) and EDM (Class 3 5)
30
Steel Distribution Poles - The Material of the
Future
31
Steel Distribution Poles - The Material of the
Future

• In Conclusion
• Steel Distribution Poles Provide
• Expected Strength
• Expected Life
• Expected Performance in
• Deflection
• Handling
• Field Use