American Iron and Steel Institute’s 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.

American Iron and Steel Institute

Designing For “Equivalency”

“Equivalency” to what?

– Expected Strength – Expected Life – Expected Performance • Deflection • • Handling Field Use American Iron and Steel Institute

Designing For “Equivalency”

• • Most pole used to date have been wood How do you design a “Steel wood pole”?

– You can’t … but you don’t want to – Instead you

design

a pole that meets minimum strength and performance requirements every time American Iron and Steel Institute

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 American Iron and Steel Institute

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 American Iron and Steel Institute

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 American Iron and Steel Institute

National Electrical Safety Code (ANSI C-2)

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

National Electrical Safety Code (ANSI C-2)

• 1941 Summary: – Material • • Steel wood – (equiv. OLF) Grade B 2.54

25% (4.0) Grade C 2.2

37.5% (2.67) American Iron and Steel Institute

National Electrical Safety Code (ANSI C-2)

• 1973 Wood was modified: – Material • • Steel wood – (equiv. OLF) – Familiar?

Grade B 2.54

25% (4.0) Grade C 2.2

50% (2.0) – wood is now lower than steel in Grade C.

• 1997 Edition introduced Strength Factors American Iron and Steel Institute

National Electrical Safety Code (ANSI C-2)

1997 Edition Grade B: Load Type Overload Strength Factor Equiv. O.L.F.

Steel Vertical 1.5 1.0 0.65

Wood Steel Wood 1.5 2.31

0.65

Transverse Wind 2.5 1.0 0.65

2.5 3.85

Ratio 0.65

Tension 1.65 1.0 American Iron and Steel Institute 0.65

1.65 2.54

0.65

National Electrical Safety Code (ANSI C-2)

1997 Edition Grade C: Strength Factor Equiv. O.L.F.

Load Type Overload Steel Wood Steel Wood Vertical 1.5 1.0 0.85

1.5 1.76

Transverse 2.2 2.06

Wind 2.2 (steel) 1.0 0.85

1.75(wood) Tension 1.1 (steel) 1.0 0.85

1.3 (wood) 1.1 1.53

Ratio 0.85

1.07

0.72

American Iron and Steel Institute

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 American Iron and Steel Institute

Designing For “Equivalency”

• “Equivalent Wood Pole” Loading (B): – ANSI Load x 2.5/4.0

Pole Class 2 3 4 5 ANSI 05.1

Loading 3700 # 3000 2400 1900 Working Load 925 # 750 600 475 “Equivalent” Steel Load 2313 # 1875 1500 1188 American Iron and Steel Institute

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 #

American Iron and Steel Institute

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#)

American Iron and Steel Institute

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” American Iron and Steel Institute

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 American Iron and Steel Institute

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 American Iron and Steel Institute

Load Deflection of Steel vs. Wood Poles (40’ Class 4, NESC Grade “B”)

Deflection of 40 ft. Class 4 (Treatment Adjustments per Table C4)

100.00

90.00

80.00

70.00

60.00

50.00

40.00

30.00

20.00

10.00

0.00

lbs.

600 lbs.

700 lbs.

800 lbs.

lbs.

lbs.

lbs.

lbs.

lbs.

lbs.

lbs.

lbs.

lbs.

lbs.

lbs.

900 1000 1100 1200 1300 1400 1500 1700 1900 2100 2300 2400

Loading (lbs.)

American Iron and Steel Institute Western Red Cedar So. Yellow Pine Steel Pole Douglas Fir

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 American Iron and Steel Institute

Weight Comparison of Wood to Steel

2500 2000 1500 1000 500 0 5 40 4 40 3 40 5 4 3 5 45 45 45

CLASS and WEIGHT

50 4 50 3 50 2 50 American Iron and Steel Institute Douglas Fir Weight, lbs.

Steel Pole Weight, lbs.

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 American Iron and Steel Institute

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 American Iron and Steel Institute

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 American Iron and Steel Institute

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 American Iron and Steel Institute

Post Insulator Test On Steel Pole

American Iron and Steel Institute

Guy Attachment Test On Steel Pole

American Iron and Steel Institute

EPRI Test On 70’ Class 2 Steel Pole

American Iron and Steel Institute

Testing at EPRI (Class 2) and EDM (Class 3 & 5)

Summary of EPRI (Class 2) and EDM (Class 3 & 5) Testing Show ing Horizontal Load Characteristics of Steel Poles 4500 4000 3500 3000 2500 2000 1500 1000 500 0 Class H1 Class 1 Class 2 Class 3 Class 4 Class 5 Class 5 American Iron and Steel Institute Class 3 Class 2

Steel Distribution Poles - The Material of the Future American Iron and Steel Institute

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 American Iron and Steel Institute