IS 5978 : 1970Code of practice for the design of wood poles for overhead power and telecommunication lines

Link points to Internet Archive / others. Not hosted by InfraLens. Details

ANSI O5.1 · EN 14229 · IEEE C2

CurrentSpecializedCode of PracticeBIMStructural Engineering · Timber and Timber Stores

Link points to Internet Archive / others. Not hosted by InfraLens. Details

IS 5978:1970 is the Indian Standard (BIS) for the design of wood poles for overhead power and telecommunication lines. This code provides guidelines for the structural design of single solid wood poles used for supporting overhead power and telecommunication lines. It covers material selection, preservative treatments, calculation of design loads like wind, and determination of permissible stresses for various timber species.

Code of practice for the design of wood poles for overhead power and telecommunication lines

Overview

Status: Current
Usage level: Specialized
Domain: Structural Engineering — Timber and Timber Stores
Type: Code of Practice
Amendments: Amendment 1 (May 1980); Amendment 2 (September 1993)

International equivalents

ANSI O5.1-2017 · American National Standards Institute (ANSI) / ASC O5, USA EN 14229:2010 · European Committee for Standardization (CEN), Europe IEEE C2-2023 (NESC) · Institute of Electrical and Electronics Engineers (IEEE), USA

Typically used with

IS 401 IS 876 IS 883

Also on InfraLens for IS 5978

5Key values 3Tables 4FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes

! The wind pressure values in Table 3 are outdated. It is crucial to use the latest version of IS 875 (Part 3) for calculating wind loads.

! The critical design section for a cantilever pole is at the ground line, where bending moment is typically maximum.

! Effective preservative treatment of timber as per IS 401 is essential for the durability and service life of the pole.

Frequently referenced clauses

Cl. 3Materials (Species of Timber)Cl. 4Preservative Treatment Cl. 5Design Considerations (Loads)Cl. 6Permissible Stresses Cl. 7Design of Poles

Updates & Amendments2 amendments

Amendment 1 (May 1980)

Amendment 2 (September 1993)

Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.

woodtimber

International Equivalents

Similar International Standards

ANSI O5.1-2017American National Standards Institute (ANSI) / ASC O5, USA

HighCurrent

Wood Poles - Specifications and Dimensions

Specifies material requirements, dimensions, defects, and fiber stress values for wood poles.

EN 14229:2010European Committee for Standardization (CEN), Europe

HighCurrent

Structural timber — Wood poles for overhead lines

European standard defining requirements for preservative-treated wood poles for overhead lines.

IEEE C2-2023 (NESC)Institute of Electrical and Electronics Engineers (IEEE), USA

MediumCurrent

National Electrical Safety Code (NESC)

Provides loading, clearance, and strength requirements for utility lines, which dictates the required pole strength.

BS 1990-1:1984British Standards Institution (BSI), UK

HighWithdrawn

Wood poles for overhead power and telecommunication lines - Part 1: Specification for untreated and treated poles

Former British standard for wood pole specification, likely a historical basis for the IS code.

Key Differences

≠IS 5978 uses an Allowable Stress Design (ASD) method with a single global Factor of Safety. Modern codes like the NESC (IEEE C2) use a Load and Resistance Factor Design (LRFD) approach, applying separate factors to different types of loads and to the material's resistance.

≠The Indian standard specifies permissible stresses for specific Indian timber species (e.g., Sal, Teak, Deodar). International standards like ANSI O5.1 list species common to their regions (e.g., Southern Pine, Douglas Fir), and EN 14229 uses a system of strength classes that are independent of species.

≠Wind load calculations in IS 5978 are based on a simplified zonal map of India (referencing IS 875:1964). Modern international practices (e.g., ASCE 7, referenced by NESC) use more complex models involving 3-second gust speeds, detailed topographic factors, and gust-effect factors for a more precise analysis.

≠ANSI O5.1 classifies poles into numbered classes (e.g., Class 1, Class 2) based on their resisting moment capacity, which simplifies selection. IS 5978 does not use this classification system, relying instead on calculations based on the pole's geometry and the timber's specific material properties.

Key Similarities

≈All standards are based on the fundamental mechanical model of the pole as a cantilever beam fixed at the groundline, subjected to transverse loads from wind and line tension.

≈There is a common emphasis on the necessity of preservative treatment to protect poles from decay and insects to ensure long-term durability and strength, with all standards referencing separate, detailed standards for treatment processes.

≈All codes acknowledge the tapered geometry of wood poles and require that strength calculations account for the changing diameter, with the critical section for bending stress typically located at the groundline.

≈The types of loads considered are fundamentally similar, including transverse wind load on the pole surface, wind load on conductors and attachments, and unbalanced longitudinal loads at angles or dead-ends.

Parameter Comparison

Parameter	IS Value	International	Source
Factor of Safety (Solid Poles, Transverse Load)	2.5	Uses Overload Capacity Factor (OCF) for specific load cases. For transverse wind load (Grade B), the OCF is 2.5.	IEEE C2 (NESC)
Basis for Material Strength	Permissible stresses based on Modulus of Rupture for specific Indian timbers (e.g., Sal) per IS 883.	Designated Fiber Stress (DFS) values assigned to species groups (e.g., Southern Pine, Douglas Fir).	ANSI O5.1-2017
Planting Depth (General Rule)	1/6 of the pole height, with specified minimums for different soil types.	10% of the pole's length plus 2 feet (0.6 m) is a common utility rule of thumb.	RUS Bulletin 1724E-200 (Common US Practice)
Wind Load Basis	Basic wind speed (steady speed) from IS 875 zonal map.	Basic wind speed (3-second gust) from detailed county-level maps per ASCE 7.	IEEE C2 (NESC) / ASCE 7
Pole Classification System	Based on length, top circumference, and timber species.	Based on strength classes (e.g., Class 1 to 10) which define a minimum horizontal load capacity.	ANSI O5.1-2017
Minimum Top Circumference (for ~9m pole)	390 mm (for 125 mm tip diameter)	~483 mm (19 inches for a 30 ft, Class 5 pole)	ANSI O5.1-2017

⚠ Verify details from original standards before use

Key Values5

Quick Reference Values

Factor of Safety on ultimate stress2.5 (Clause 7.1)

Permissible Bending Stress (Group A Timber, Inside Location)125 kgf/cm² (Table 2)

Permissible Bending Stress (Group B Timber, Inside Location)100 kgf/cm² (Table 2)

Permissible Bending Stress (Group C Timber, Inside Location)75 kgf/cm² (Table 2)

Basic Wind Pressure (High Intensity, up to 15m height)150 kgf/m² (Table 3)

Key Formulas

fb = M / Z ≤ Fb — Bending stress check at ground line, where M is max bending moment and Z is section modulus

M = P1*h1 + P2*h2 + ... — Calculation of Bending Moment from various transverse loads (wind on pole, wind on conductor, etc.)

Tables & Referenced Sections

Key Tables

Table 1 - Grouping of Indian Timbers for Poles

Table 2 - Permissible Stresses for Wood Poles (Ultimate Stresses and Modulus of Elasticity)

Table 3 - Wind Pressure on Smooth Cylindrical Surfaces

Key Clauses

Clause 3 - Materials (Species of Timber)

Clause 4 - Preservative Treatment

Clause 5 - Design Considerations (Loads)

Clause 6 - Permissible Stresses

Clause 7 - Design of Poles

Frequently Asked Questions4

What is the required factor of safety for designing wood poles?+

A factor of safety of 2.5 on the ultimate stress of the timber species used (Clause 7.1).

Which types of wood are recommended for poles?+

The code groups timbers into A, B, and C. Group A (e.g., Sal), having the highest strength, is most preferred, followed by Group B (e.g., Kail, Teak) (Table 1).

What is the permissible bending stress for Sal wood poles?+

For Sal (Group A), the permissible stress in bending for 'Inside Location' is 125 kgf/cm² (Table 2).

How deep should a wood pole be planted?+

This code does not specify planting depth but refers to IS 1039 for guidance. A common rule is 1/6th of the pole's total length.

QA/QC Inspection Templates

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QA/QC templates coming soon for this code.

Browse all 300 templates →

IS 5978 : 1970Code of practice for the design of wood poles for overhead power and telecommunication lines

PDF Google Compare BIS Portal

Link points to Internet Archive / others. Not hosted by InfraLens. Details

ANSI O5.1 · EN 14229 · IEEE C2

CurrentSpecializedCode of PracticeBIMStructural Engineering · Timber and Timber Stores

PDF Google Compare BIS Portal

Link points to Internet Archive / others. Not hosted by InfraLens. Details

Code of practice for the design of wood poles for overhead power and telecommunication lines

Overview

Status: Current
Usage level: Specialized
Domain: Structural Engineering — Timber and Timber Stores
Type: Code of Practice
Amendments: Amendment 1 (May 1980); Amendment 2 (September 1993)

International equivalents

Typically used with

IS 401 IS 876 IS 883

Also on InfraLens for IS 5978

5Key values 3Tables 4FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes

! The wind pressure values in Table 3 are outdated. It is crucial to use the latest version of IS 875 (Part 3) for calculating wind loads.

! The critical design section for a cantilever pole is at the ground line, where bending moment is typically maximum.

! Effective preservative treatment of timber as per IS 401 is essential for the durability and service life of the pole.

Frequently referenced clauses

Cl. 3Materials (Species of Timber)Cl. 4Preservative Treatment Cl. 5Design Considerations (Loads)Cl. 6Permissible Stresses Cl. 7Design of Poles

Updates & Amendments2 amendments

Amendment 1 (May 1980)

Amendment 2 (September 1993)

Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.

woodtimber

International Equivalents

Similar International Standards

ANSI O5.1-2017American National Standards Institute (ANSI) / ASC O5, USA

HighCurrent

Wood Poles - Specifications and Dimensions

Specifies material requirements, dimensions, defects, and fiber stress values for wood poles.

EN 14229:2010European Committee for Standardization (CEN), Europe

HighCurrent

Structural timber — Wood poles for overhead lines

European standard defining requirements for preservative-treated wood poles for overhead lines.

IEEE C2-2023 (NESC)Institute of Electrical and Electronics Engineers (IEEE), USA

MediumCurrent

National Electrical Safety Code (NESC)

Provides loading, clearance, and strength requirements for utility lines, which dictates the required pole strength.

BS 1990-1:1984British Standards Institution (BSI), UK

HighWithdrawn

Wood poles for overhead power and telecommunication lines - Part 1: Specification for untreated and treated poles

Former British standard for wood pole specification, likely a historical basis for the IS code.

Key Differences

Key Similarities

≈All standards are based on the fundamental mechanical model of the pole as a cantilever beam fixed at the groundline, subjected to transverse loads from wind and line tension.

Parameter Comparison

Parameter	IS Value	International	Source
Factor of Safety (Solid Poles, Transverse Load)	2.5	Uses Overload Capacity Factor (OCF) for specific load cases. For transverse wind load (Grade B), the OCF is 2.5.	IEEE C2 (NESC)
Basis for Material Strength	Permissible stresses based on Modulus of Rupture for specific Indian timbers (e.g., Sal) per IS 883.	Designated Fiber Stress (DFS) values assigned to species groups (e.g., Southern Pine, Douglas Fir).	ANSI O5.1-2017
Planting Depth (General Rule)	1/6 of the pole height, with specified minimums for different soil types.	10% of the pole's length plus 2 feet (0.6 m) is a common utility rule of thumb.	RUS Bulletin 1724E-200 (Common US Practice)
Wind Load Basis	Basic wind speed (steady speed) from IS 875 zonal map.	Basic wind speed (3-second gust) from detailed county-level maps per ASCE 7.	IEEE C2 (NESC) / ASCE 7
Pole Classification System	Based on length, top circumference, and timber species.	Based on strength classes (e.g., Class 1 to 10) which define a minimum horizontal load capacity.	ANSI O5.1-2017
Minimum Top Circumference (for ~9m pole)	390 mm (for 125 mm tip diameter)	~483 mm (19 inches for a 30 ft, Class 5 pole)	ANSI O5.1-2017

⚠ Verify details from original standards before use

Key Values5

Quick Reference Values

Factor of Safety on ultimate stress2.5 (Clause 7.1)

Permissible Bending Stress (Group A Timber, Inside Location)125 kgf/cm² (Table 2)

Permissible Bending Stress (Group B Timber, Inside Location)100 kgf/cm² (Table 2)

Permissible Bending Stress (Group C Timber, Inside Location)75 kgf/cm² (Table 2)

Basic Wind Pressure (High Intensity, up to 15m height)150 kgf/m² (Table 3)

Key Formulas

fb = M / Z ≤ Fb — Bending stress check at ground line, where M is max bending moment and Z is section modulus

M = P1*h1 + P2*h2 + ... — Calculation of Bending Moment from various transverse loads (wind on pole, wind on conductor, etc.)

Tables & Referenced Sections

Key Tables

Table 1 - Grouping of Indian Timbers for Poles

Table 2 - Permissible Stresses for Wood Poles (Ultimate Stresses and Modulus of Elasticity)

Table 3 - Wind Pressure on Smooth Cylindrical Surfaces

Key Clauses

Clause 3 - Materials (Species of Timber)

Clause 4 - Preservative Treatment

Clause 5 - Design Considerations (Loads)

Clause 6 - Permissible Stresses

Clause 7 - Design of Poles

Frequently Asked Questions4

What is the required factor of safety for designing wood poles?+

A factor of safety of 2.5 on the ultimate stress of the timber species used (Clause 7.1).

Which types of wood are recommended for poles?+

The code groups timbers into A, B, and C. Group A (e.g., Sal), having the highest strength, is most preferred, followed by Group B (e.g., Kail, Teak) (Table 1).

What is the permissible bending stress for Sal wood poles?+

For Sal (Group A), the permissible stress in bending for 'Inside Location' is 125 kgf/cm² (Table 2).

How deep should a wood pole be planted?+

This code does not specify planting depth but refers to IS 1039 for guidance. A common rule is 1/6th of the pole's total length.

QA/QC Inspection Templates

📋

QA/QC templates coming soon for this code.

Browse all 300 templates →

IS 5978 : 1970Code of practice for the design of wood poles for overhead power and telecommunication lines

Overview

International Equivalents

Key Values5

Tables & Referenced Sections

Related Resources on InfraLens

Frequently Asked Questions4

QA/QC Inspection Templates

IS 5978 : 1970Code of practice for the design of wood poles for overhead power and telecommunication lines

Overview

International Equivalents

Key Values5

Tables & Referenced Sections

Related Resources on InfraLens

Frequently Asked Questions4

QA/QC Inspection Templates