national wood pole standards€¦ · 2 benefits of wood as a utility pole material • long-life...

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National Wood Pole

Standards

Nelson G. Bingel III – NESC Chairman

President(678) [email protected]

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Benefits of Wood as a Utility Pole Material

• Long-Life Span• ~45 years national average without remedial treatment

• Lowest cost• Both initial and full life-cycle costs

• Proven Performance • “Go to” overhead line construction material since the

early 1900’s

• Climb-ability• Ability to service attachments without heavy equipment

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• Supply Chain is Proven• Even in natural disaster events where demand is high, the wood

pole industry has provided poles in required timeline.

• Beneficial Physical Properties• Good insulator, resilience to wind and mechanical impacts

• Easy Maintenance and Modification in service

• “Green”• a treated wood pole has a reduced environmental impact when

compared to other utility pole materials.

• A renewable and plentiful resource

“10 Features Often Overlooked About the Extraordinary Wood Pole.” North American Wood Pole Council. www.woodpoles.org

Benefits of Wood as a Utility Pole Material

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ANSI

American National Standards Institute

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ANSI


ANSI accredits the procedures of standards developing organizations

National consensus standards

Openness, balance, consensus and due process

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ASC O5 Committee

American Standards Committee O5

USERS

PRODUCERS

GENERAL INTEREST


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ASC O5 NESC

Accredited Standards

Committee O5:

Standards for Wood

Utility Structures

• Secretariat: AWPA

• Revised: 5 year cycle

• Founded in 1924

National Wood Pole Standards

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ASC O5 Standards http://asco5.org/standards/

O5.4 - 2009 Naturally Durable Hardwood Poles

O5.5 - 2010 Wood Ground Wire Moulding

O5.6 - 2010 Solid Sawn Naturally Durable Hardwood Crossarms & Braces

O5.TR.01-2004 Photographic Manual of Wood Pole Characteristics

Poles Glu-Lam Crossarms

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http://asco5.org/

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http://asco5.org/standards/

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Scope

Single Pole

Simple Cantilever

Transverse

Groundline

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Maximum Stress Point

Max Stress @ 1.5 Diameter Load Point

Solid, Round, Tapered, Cantilever

Distribution Usually Groundline

Load(Wind Force on Wires, Equip., etc.)

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ANSI O5.1 – Wood Poles

Wood

Quality

Class

Loads

Pole

Dimensions

Fiber

Strength

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Wood Quality

• Allowable knots

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Wood Quality

• Sweep

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Wood Quality

• Growth Rings

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Pole Marking & Code Letters

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Pole Marking & Code Letters

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Transverse Wind Loads

Ice

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Class Loads

2 ft Lc

Horizontal

Class Load (lb)

10 370

9 740

7 1,200

6 1,500

5 1,900

4 2,400

3 3,000

2 3,700

1 4,500

H1 5,400

H2 6,400

H3 7,500

H4 8,700

H5 10,000

H6 11,400

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Class Loads

2 ft Lc

Telco

Distribution

Transmission

Horizontal

Class Load (lb)

10 370

9 740

7 1,200

6 1,500

5 1,900

4 2,400

3 3,000

2 3,700

1 4,500

H1 5,400

H2 6,400

H3 7,500

H4 8,700

H5 10,000

H6 11,400

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Strengths are Average Values

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Pole Populations

Wood Poles

Steel Poles

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P

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Lc

D

2 ft

Class 1 4,500 lb

Class 2 3,700 lb

Class 3 3,000 lb

Class 4 2,400 lb

Class 5 1,900 lb

Applied Bending Load

Applied Bending Load =

Lc x D (ft-lb)

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L x D = Bending Moment (ft-lb)

76,800 ft-lb

2400 lb

32 ft

40 ft Class 4

41 ft

98,400 ft-lb

2400 lb

50 ft Class 4

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Lc

Fiber Strength

Compression

(psi)

Tension

(psi)Fiber Strength

Bending Capacity =

k x fiber strength x C3 (ft-lb)

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Circumference3 Effect

MG/L = .000264 x Fiber Stress x Circumference 3

26”34”

37,120 ft-lb83,010 ft-lb

Circumference Increase - 30%

Bending Capacity Increase - 123%

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Circumference3 Effect

MG/L = .000264 x Fiber Stress x Circumference 3

26”34”

37,120 ft-lb83,010 ft-lb

Circumference Increase - 30%

Bending Capacity Increase - 123%

80-90%

Pole’s Bending Strength

In The Outer 2-3” Of Shell!

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Table 1 – Designated Fiber Strength

Group AAir Seasoning

Group BBoulton Drying

Group CSteam Conditioning

Group DKiln Drying

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Southern Yellow Pine 8,000 psi

Douglas fir 8,000 psi

Western red cedar 6,000 psi

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Pole Species

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Distribution:Southern Yellow Pine

Transmission:Douglas fir

Western red cedar

Southern Pine

Distribution:Douglas fir

TransmissionDouglas fir

Western red cedar

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1) The effects of conditioning on fiber strength have been accounted for in the Table 1

values provided that conditioning was performed within the limits herein prescribed.

4) The designated fiber strength represents a mean, groundline, fiber strength value

with a coefficient of variation equal to 0.20.

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Through-boring

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Oregon State University

-Through-Boring Project-

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Through-boring

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5) Where Douglas-fir (coastal or Interior North) are through-bored prior to treatment, to

account for the process, the designated fiber strength shall be reduced 5% to 7600 psi.

4) The designated fiber strength represents a mean, groundline, fiber strength value

with a coefficient of variation equal to 0.20.

1) The effects of conditioning on fiber strength have been accounted for in the Table 1

values provided that conditioning was performed within the limits herein prescribed.

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2017 Table 1 to add MOE

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1) The fiber strength and MOE values in Table 1 apply to wood utility poles meeting this

standard. The effects of conditioning on fiber strength and MOE have been accounted for

………….

7) The Modulus of Elasticity (MOE) represents a mean value.

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Circumference Dimensions

TIP

6ft

G/L

Bending Capacity =


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Circumference Dimension Tables

1) The figures in this column are not recommended embedment depths; rather,

these values are intended for use only when a definition of groundline is necessary

in order to apply requirements relating to scars, straightness, etc.

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Annex B: Groundline Stresses

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Minimum circumferences specified at 6 feet from the butt

Were calculated so each species in a given class

Can support the class horizontal load applied 2 ft from the tip

Bending Capacity =


Applied Bending Load =

Lc x D (ft-lb)

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Pole Dimension Table

(in)

Southern Pine and Douglas Fir

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(in)

Southern Pine and Douglas FirApplied Bending Load=

Class Load x Distance

2,400 lbs x 32 ft =

76,800 ft-lbs

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(in)

Southern Pine and Douglas FirApplied Bending Load=

Class Load x Distance

Bending Capacity =

k x fiber strength x C3

.000264 x 8000 x 33.53 =

79,401 ft-lbs

2,400 lbs x 32 ft =

76,800 ft-lbs

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40 ft Class 4 Poles

Douglas fir

(8000 psi)

36 1/2”

Western Red Cedar

(6000 psi)

33 1/2”

2400 lb

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Average circumference tapers

in the groundline zone of a pole

Note 7

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ANSI O5.1 Summary

2 ft Lc

Bending

Capacity = k x fiber strength x C3 (ft-lb)

All Species

Same Length & Class

Similar Load Capacity

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Fiber Strength Values

1965 Publication

Forest Products Lab

Fiber Strength

Derivation

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FPL 39 Table 4Final Adopted Fiber Strengths

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FPL 39 Table 4

Final Adopted Fiber Strengths

Near 5% Lower Exclusion Limit

Of Actual Average Bending Strength

Of Three Pole Groups

For Grade B Construction

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Annex C Data < 50 ft

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Annex C Data – 50 ft +

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Full Scale Break Tests

02000400060008000

10000120001400016000

15 25 35 45 55 65 75 85

MO

RG

L (

psi

)

Groundline Circumference (GC) (in)

Douglas Fir Poles

Mean = 8380 psiL5 = 6401 psi Mean = 6630 psi

L5 = 4825 psi

ASTM

EPRI

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Full Scale Break Tests

02000400060008000

10000120001400016000

15 25 35 45 55 65 75 85

MO

RG

L (

psi

)

Groundline Circumference (GC) (in)

Douglas Fir Poles

Mean = 8380 psiL5 = 6401 psi Mean = 6630 psi

L5 = 4825 psi

ASTM

EPRI

No Changeto

Previous Fiber Strengths

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Annex A

Fiber Stress Height Effect

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Annex A

Fiber Stress Height Effect

Round timbers are known to

decrease in ultimate unit strength

with height above ground.

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Actual Pole Dimensions

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??

????

???

?

??

?

?

?

?

?

?? ?

?

??

????

?

?

?? ? ?

?

CA

TX

NY

FL

IL

PA

OH

MI

NJ

GA

NC

VA

MA

IN

WA

TN

MO

WI

MD

AZ

MN

LA

AL

CO

KY

SC

OK

OR

CT

IA

MS

KS

AR

UT

NV

NM

WV

NE

ID

ME

NH

RI

MT

DE

SD

ND

VT

DC

WY

Sample Locations? Coastal Douglas Fir (8)

? Coastal DF & Western Red (3)

? Northern Red Pine (3)

? Southern Yellow Pine (16)

?Western Red Cedar (5)

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• Coastal Douglas fir 6,997 poles9 Producers; 11 Locations

• Southern Yellow Pine 6,634 poles

11 Producers; 16 Locations

• Western Red Cedar 6,982 poles


• Northern Red Pine 2,266 poles


Grand Total 22,859 poles

Pole Circumference Data

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Fiber Stress Height Effect (FSHE)

• Tips average 1.5 to 2 classes larger

• Poles 55 ft and shorter• Maximum stress is usually at G/L

– FSHE not applied

• Maximum stress for guyed poles may be above G/L– Oversize offsets fiber stress height effect

• Poles 60 ft and taller• If maximum stress is at the G/L, no FSHE

• If maximum stress is above ground, tables for reduction

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ASC O5 Standards http://asco5.org/standards/

O5.4 - 2009 Naturally Durable Hardwood Poles

O5.5 - 2010 Wood Ground Wire Moulding

O5.6 - 2010 Solid Sawn Naturally Durable Hardwood Crossarms & Braces

O5.TR.01-2004 Photographic Manual of Wood Pole Characteristics

Poles Glu-Lam Crossarms

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ASC O5 NESC

Accredited Standards

Committee O5:

Standards for Wood

Utility Structures

• Secretariat: AWPA


• Founded in 1924

National Wood Pole Standards

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National Overhead Line Standard

ANSI C2:

National Electrical

Safety Code

• Secretariat: IEEE (Institute of Electrical and

Electronics Engineers)


• Established in 1915

NESC

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NESC Committee Structure

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Chairman Vice Chair Secretary-IEEE

25 – 35 Members

Main

Committee

Executive

Subcommittee

Technical

Subcommittees

Chairman Secretary

6 - 10 Members

Chairman Secretary

SC 1 – Coordination; Sections 1,2,3

SC 2 – Grounding

SC 3 – Substations

SC 4 – Overhead Lines – Clearances

SC 5 – Overhead Lines – Strength & Loading

SC 7 – Underground Lines

SC 8 – Work Rules

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Purpose of the NESC

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B. NESC rules contain the basic provisions, under

specified conditions, that are considered necessary for

the safeguarding of:

1. The Public

2. Utility workers (employees and contractors), and

3. Utility facilities

C. This code is not intended as a design specification or as

an instruction manual.

Purpose of the NESC

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NESC Committee Structure

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Chairman Vice Chair Secretary-IEEE

25 – 35 Members

Main

Committee

Executive

Subcommittee

Technical

Subcommittees

Chairman Secretary

6 - 10 Members

Chairman Secretary

SC 1 – Coordination; Sections 1,2,3

SC 2 – Grounding

SC 3 – Substations

SC 4 – Overhead Lines – Clearances

SC 5 – Overhead Lines – Strength & Loading

SC 7 – Underground Lines

SC 8 – Work Rules

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Section 24Grades of Construction

Section 25Loading for Grade B&C

Section 26Strength requirements

• Grades B, C & N

(B is the highest)

• Load Factors

• Rule 250B:

Combined ice and Wind

District loading

• Rule 250C:

Extreme wind Loading

• Rule 250D:

Extreme Ice with concurrent

wind loading

• Strength Factors

Overhead Lines Subcommittee 5

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Section 24Grades of Construction

Section 25Loading for Grade B&C

Section 26Strength requirements

• Grades B, C & N

(B is the highest)

• Load Factors

• Rule 250B:

Combined ice and Wind

District loading

• Rule 250C:

Extreme wind Loading

• Rule 250D:

Extreme Ice with concurrent

wind loading

• Strength Factors

Overhead Lines Subcommittee 5

Section 27Insulators

• Electrical Strength

• Mechanical Strength

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Section 24: Grades of Construction

• Grade B: (3.85 SF)• Crossing Limited Access Highways

• Crossing Railways

• Crossing Navigable Waterways

• Grade C: (2.06 SF)• All other standard construction

• Grade N: (Strength shall exceed expected loads)• Mainly used for temporary and emergency construction

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TRANSVERSE

V

E

R

T

I

C

A

L

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Section 25 – Loadings for Grade B & C

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Wire with Ice

Transverse Loading Usually Governs

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Wind Bending Loads On:

Wires

Ice

Pole

Equipment

Offset Bending Loads

Wire Tension

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Calculating Transverse Loads

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Section 25: Loading for Grade B & C

• Rule 250B: District Loading Combined Ice and Wind

• Rule 250C: Extreme Wind Loading

(60ft Exemption)

• Rule 250D: Extreme Ice

With Concurrent Wind Loading

(60ft Exemption)

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NESC District Loading

½” Ice – 40 mph

¼” Ice – 40 mph

0” Ice – 60 mph40 mph = 4 lbs/sqft

60 mph = 9 lbs/sqft

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Winter Storm

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¼” Ice

40 mph

Medium Loading District

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Wind Load Increase per Wire Sizes

0.75” 1.50” 3.00”

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Double wire diameter = Double the load

+100% +200%

2x2x

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1.25” 2.00” 3.50”

+67% +33% +17%

Wind Load Increase With 0.25” Radial Ice

1.50” 3.00”

.25” Ice

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0.75”

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District Loads vs Wire Size

0

1

2

3

4

5

6

7

8

9

4ACSR 1/0 336 556

REL

ATIV

E LO

AD

CONDUCTOR (SMALLEST TO LARGEST)

NESC-L

NESC-M

NESC-H

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No ICE

1/4” ICE

1/2” ICE

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Deterministic

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Extreme Wind– Rule 250C(60 ft. Exclusion)

85 mph = 18.5 lbs/sqft

90 mph = 21 lbs/sqft



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Summer Storm

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Extreme Ice with Concurrent Wind –Rule 250D(60 ft. Exclusion)

Winter Storm

Wind Speeds

30 mph

40 mph

50 mph

60 mph

Radial

Ice

0”

0.25”

0.5”

0.75”

1.0”

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• Rule 250C: Extreme Wind Loading

(60ft Exemption)

• Rule 250D: Extreme Ice

With Concurrent Wind Loading

(60ft Exemption)

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Deterministic

Probabilistic

Probabilistic

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Section 25 Load Cases

• Rule 250 B - Combined Ice & Wind

– Light 0” Ice 60 mph

– Medium ¼” Ice 40 mph

– Heavy ½” Ice 40 mph

– Loads to be Factored

• Rule 250 C – Extreme Wind

– Poles Taller than 60 feet Above Ground

– Wind only (no ice)

– Ultimate Load with probability of occurrence

• Rule 250 D – Extreme Ice with Wind

– Poles Taller than 60 feet Above Ground

– Ice Thickness with Concurrent Wind

– Ultimate Load with probability of occurrence

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StrengthPole Strength x SF

Pole Strength x SFAlternate Method

Strength

Load

>>

Storm Load x 4 (B)

Storm Load x 2 (C)>>

Pole Strength

Pole Strength

LoadStorm Load x LF (B)

Storm Load x LF (C)

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Grade B Grade Cx Grade CR

ule

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0B

Vertical Loads 1.50 1.90 1.90

Transverse Loads

(wind) 2.50 2.20 1.75

Longitudinal

Loads 1.10 No Req. No Req.

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0C

Wind Loads 1.00 1.00 1.00

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0D Ice and Wind

loads1.00 1.00 1.00

Section 25: Table 253.1-Load Factors

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Section 26: Strength Factors

Grade B Grade CR

ule

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0B Metal Structures 1.0 1.0

Wood Structures 0.65 0.85

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0C

& 2

50

D

Metal Structures 1.00 1.00

Wood Structures 0.75 0.75

Fiber Strength (ANSI)

× Strength Factor (NESC)=

Allowable Stress of Pole

Table 261-1

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StrengthPole Strength x SF

Pole Strength x SFAlternate Method

Strength

Load

>>

Storm Load x 4 (B)


Pole Strength

Pole Strength

LoadStorm Load x LF (B)

Storm Load x LF (C)

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StrengthPole Strength x .65

Pole Strength x .85Alternate Method

Strength

Load

>>

Storm Load x 4 (B)


Pole Strength

Pole Strength

LoadStorm Load x 2.5 (B)

Storm Load x 1.75 (C)

3.85

2.06

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Section 24: Grades of Construction

• Grade B: (3.85 SF)• Crossing Limited Access Highways

• Crossing Railways

• Crossing Navigable Waterways

• Grade C: (2.06 SF)• All other standard construction

• Grade N: (Strength shall exceed expected loads)• Mainly used for temporary and emergency construction

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Equate the

Total Storm Load

to a

Single Horizontal Load

applied

2 feet from the tip.

900 lb

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900 lb Storm Load

x 3.85 (Grade B)

Class 1 4500 lb

Class 2 3700 lb

Class 3 3000 lb

Class 4 2400 lb

Class 5 1900 lb= 3465 lb

NESC ANSI O5.1

Load < Strength

Grade B

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900 lb Storm Load

x 2.06 (Grade C)

= 1854 lb

NESC ANSI O5.1

Load < Strength

Grade C

Class 1 4500 lb

Class 2 3700 lb

Class 3 3000 lb

Class 4 2400 lb

Class 5 1900 lb

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IEEE Online Courses – MOOC’s

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MOOC #1 NESC Overview

MOOC #2 2017 Changes

http://standards.ieee.org/about/nesc/

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Technical Subcommittees

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SC1 - Coordination between technical subcommittees

Sections 1, 2 and 3

SC2 - Grounding Methods - Section 9

SC3 - Electric Supply Stations - Sections 10-19

SC4 - Overhead Lines - Clearances - Section 20-23

SC5 - Overhead Lines - Strength and Loading

Sections 24-27

SC7 - Underground Lines - Sections 30-39

SC8 - Work Rules - Sections 40-43

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Online Courses – MOOC’s

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MOOC #1 NESC Overview

MOOC #2 2017 Changes

MOOC #3 Grounding Methods

MOOC #4 Electric Supply Stations

MOOC #5 Overhead Lines – Clearances and S&L

MOOC #6 Underground Lines

MOOC #7 Work Rules

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NESC Mobile App

• Mobile device or tablet

• iOS, Android, Windows

• Full printed document

• Enhanced features

– Instant access to formulas, equations

and calculations with context

– Quick look-up of terms

– Quick access to sections

Released !!!!

http://standards.ieee.org/about/nesc/mobile_app.html

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Tables & Equations

Home Page Table of Contents

NESC Mobile App

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Search the NESC Search IEEE

NESC Mobile App

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National Wood Pole

Standards

Nelson G. Bingel III – NESC Chairman

President(678) [email protected]

national wood pole standards€¦ · 2 benefits of wood as a utility pole material • long-life...

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