jointed wood poles for overhead power and telecommunication lines
1970 Edition

Application Scope of IS 6056: Key Specifications and Tables

Scope (Clause 4.2):

• For poles with intermediate lengths listed in Table 1, adopt the circumference of the next larger pole size.
• Final test and analysis figures should be rounded following IS 2-1960 with the same precision as specified.

Critical Table: Overall Dimensions for Wire-Bound Lap Jointed Poles (Clause 11.2.2)

Additional Notes:

• Definitions conform to IS 707-19.
• Updated references for Clauses 7.5 and 8.

This ensures accurate pole sizing and jointing within the standard's framework.

IS 6056 - Terminology and Essential Specifications Overview

1. Definitions (Clause 2.0)

• Definitions provided in Clauses 2.1, 2.2, and IS 707-19 are applicable.
• Classification of wood poles is based on length, circumference, and joint configurations.

2. Pole Dimensions (Clause 4.2, Table 1)

• Poles are categorized from Class 1 to Class 7.
• Specified minimum circumference at the base and the upper end of the pole.
• For lengths between standard sizes, use the circumference corresponding to the next higher size.

(Refer to Table 1 for comprehensive details by class and group)

3. Timber Species Classification (Appendix A, Clause 7.1)

• Species are grouped into A, B, and C based on durability and availability.
• Average density at 12% moisture content (kg/m³) is specified.

Species marked with an asterisk indicate non-durable timber.

Diagram: Pole Classification and Dimension Overview

flowchart TD
    Pole[Wood Pole] --> Class[Classes 1 to 7]
    Class --> Dimensions[Dimensions: Length & Circumference]
    Class --> Joints[Joint Types]
    Pole --> SpeciesGroups[Timber Groups A, B, C]
    SpeciesGroups --> Details[Details and Properties]

IS 6056 - Timber Groupings and Mechanical Properties for Poles

Timber Groups Based on Modulus of Rupture (Clause 3.1)

Species and Typical Density (Appendix A Excerpt)

Important Notes:

• Strength classification applies to timber with moisture content exceeding 25% (green condition).
• Species with an asterisk (*) are considered non-durable.
• Testing methods for modulus of rupture are detailed in IS 1708-1969.

graph TD
  TimberGroups[Timber Groups] --> GroupA[Group A: Very High Strength (≥850 kg/cm²)]
  TimberGroups --> GroupB[Group B: High Strength (630–850 kg/cm²)]
  TimberGroups --> GroupC[Group C: Moderate Strength (450–630 kg/cm²)]
  GroupA --> Sal[Shorea robusta]
  GroupB --> Teak[Tectona grandis]
  GroupC --> Chir[Pinus roxburghii]

This classification facilitates selection of timber species for poles based on mechanical strength and longevity.

IS 6056 - Load Estimations and Testing Protocols for Wood Poles

Load Assumptions (Based on IS 6056 and Related Standards)

• Dead Load (DL): Weight of the pole and attached components.
• Live Load (LL): As defined in IS 875 (Part 2), depending on line usage.
• Wind Load (WL): Calculated according to IS 875 (Part 3), considering pole shape and exposure.
• Impact Load: Typically 25% to 50% of live load to account for dynamic effects.
• Load Combinations: Follow IS 800 or IS 456 for factoring combined loads.

Testing Methods

• Tensile Testing: Determines yield strength, ultimate strength, and elongation properties.
• Bending Tests: Assess ductility and weld integrity.
• Hydrostatic Testing: Applies pressure to tubular poles to check for leaks.
• Non-Destructive Testing (NDT): Includes radiography and ultrasonic inspections to detect weld defects.

Key Formulas:

• Axial Load Capacity: [ P = A \times f_y ] Where:

  • (P) = axial load capacity
  • (A) = cross-sectional area
  • (f_y) = steel yield strength

• Moment of Inertia for Circular Tubes: [ I = \frac{\pi}{64} (D^4 - d^4) ] Where:

  • (D) = outer diameter
  • (d) = inner diameter

Example Table: Allowable Load Parameters

flowchart LR
    Loads[Load Assumptions] --> DL[Dead Load]
    Loads --> LL[Live Load]
    Loads --> WL[Wind Load]
    Loads --> IL[Impact Load]
    Tests[Testing Methods] --> Tensile[Tensile Test]
    Tests --> Bend[Bend Test]
    Tests --> Hydro[Hydrostatic Test]
    Tests --> NDT[Non-Destructive Testing]

Preservative Treatment Guidelines per IS 6056 and IS 401-1967

1. Initial Preparation (Clause 6.1):

• Remove all bark completely and trim branches flush with the pole surface (see Clause 5.1).
• Immediately apply prophylactic treatments according to IS 401-1967 to prevent fungal and insect infestation.
• Store treated components on treated support blocks at a height of at least 15 cm above ground, ensuring proper drainage and cleanliness.

2. Impregnation Treatment (Clause 7.1):

• All components must be pressure-treated to fully impregnate the sapwood and as much heartwood as feasible in non-durable species.
• Preservatives such as creosote or copper-chrome-arsenic compounds should be used as specified by IS 401-1967.
• Pressure treatment guarantees deep penetration for enhanced longevity.

3. Timber Species Groupings (Appendix A):

• Group A (Non-durable species) require thorough treatment examples include:
  • Bruguiera spp. (BRU), density ~893 kg/m³
  • Hopea perviflora (HOP), density ~995 kg/m³
  • Kayea assamica (KAY), density ~801 kg/m³
• Groups B and C species are more naturally durable but may still need treatment depending on application.

Extracted Table: Selected Non-Durable Species (Group A)

Treatment Process Flowchart

flowchart TD
    Prepare[Preparation of Components] --> RemoveBark[Complete Bark Removal & Branch Dressing]
    RemoveBark --> Prophylactic[Apply Prophylactic Treatment (IS 401)]
    Prophylactic --> PressureTreat[Pressure Preservative Treatment]
    PressureTreat --> Storage[Store on Treated Crossers ≥ 15 cm Above Ground]

IS 6056: General Specifications for Jointed Wooden Poles

1. Pole Shape and Straightness (Clause 10.3.11)

• Each segment of the pole must be fairly straight.
• Curvature is permitted only in a single plane and direction.
• When assembled, the curvatures of the segments must be in the same plane but in opposite directions.
• The sum of maximum deviations (X1 + X2) from straightness must not exceed half the average diameter of the pole.

2. Dimensions for Jointed Poles (Clause 11.2.2, Table 11.1)

Important Points:

• Overlap length is vital to ensure joint strength and structural continuity.
• Assembly is done so that curvatures counterbalance each other, maintaining overall straightness.
• Accurate dimensions are crucial for load distribution and mechanical stability.

flowchart LR
    TopSection[Upper Segment] -->|Overlap| BottomSection[Lower Segment]
    BottomSection --> JointedPole[Assembled Jointed Pole]
    subgraph CurveControl[Curvature Management]
        direction TB
        X1[Deviation in Upper Segment]
        X2[Deviation in Lower Segment]
    end
    CurveControl --> JointedPole

IS 6056 - Specifications for Dimensions and Permissible Tolerances of Jointed Wood Poles

1. Pole Dimensions (Clause 4.2 & Table 1)

• Poles are categorized into seven classes (Class 1 through Class 7).
• Minimum circumference at the base of the lower section varies according to class and length.
• Example: For a 6-meter pole (Class 1):
  • Circumference A: 62 cm
  • Circumference B: 65 cm
  • Circumference C: 72 cm
• For lengths between standard sizes, use the circumference of the next larger pole.

2. Joint Section Requirements (Clause 8.1.2)

• Sections to be joined should have roughly equal girth at the joint.
• This maintains uniform taper and consistent load classification across the joint.

3. Joint Lengths (Clause 11.2.2 & Table 11.1)

Summary:

• Consult Table 1 for minimum circumferences at ground level.
• Ensure uniform circumference at the joint sections.
• Adhere to minimum overlap lengths for secure jointing.

Quality Requirements for Timber Sections as per IS 6056

1. Species Grouping and Physical Properties (Appendix A)

• Timber species are divided into groups A, B, and C depending on durability and availability.
• Important attributes include average density at 12% moisture content (kg/m³).
• Examples:
  • Group A: Hopea perviflora (995 kg/m³), Mesua ferrea (995 kg/m³)
  • Group B: Casuarina equisetifolia (850 kg/m³), Sissoo (770 kg/m³)
  • Group C: Cedrus deodara (545 kg/m³), Pinus roxburghii (550 kg/m³)

2. Dimensional Criteria (Clause 4.2, Table 1)

• Minimum circumferences at the base and top of the upper section are prescribed per class and group.
• For example, a 6-meter pole in Group A requires:
  • Minimum base circumference: 62 cm
  • Minimum top circumference: 50 cm

3. Additional Quality Notes

• Species marked with an asterisk (*) are categorized as non-durable.
• Moisture content is standardized at 12% for weight and strength calculations.
• Joint dimensions and species selection must align with group classifications for strength and durability.

flowchart TD
    TimberSpecies --> Grouping{Group}
    Grouping -->|A| HighDurability[High Density and Durability]
    Grouping -->|B| MediumDurability[Medium Density]
    Grouping -->|C| LowDurability[Lower Density and Durability]
    HighDurability --> HighCircumference[Higher Minimum Circumference]
    MediumDurability --> MediumCircumference[Medium Minimum Circumference]
    LowDurability --> LowCircumference[Lower Minimum Circumference]

Summary: Select timber species from Appendix A according to group; verify minimum circumferences from Table 1 based on pole class and size; maintain moisture content at 12%.

IS 6056: Classification of Jointed Poles and Jointing Techniques

1. Joint Types (Clause 11)

• Butt Jointed Poles (Clause 11.4.1):

  • Upper and lower pole sections joined end-to-end (butt to butt).
  • Secured with four angle irons sized 60x60x5 mm.
  • Two opposite angle irons are bolted at the joint for fixation.

• Wire-Bound Lap Joints (Clause 11.2.2 & Table 11.1):

  • Sections overlap and are bound with wire.
  • Overlap length depends on overall pole length.

2. Key Dimensional Data from Table 11.1 (meters)

3. Straightness and Curvature (Clause 10.3.11)

• Curvature is only acceptable in one plane and in one direction per pole segment.
• When assembled, the segments' curvatures must be oriented in opposite directions in the same plane.
• The combined maximum deviation (X1 + X2) must not exceed half the average diameter of the pole.

4. Illustrations of Joint Types

• Wire-Bound Lap Joint (Figure 2)
• Z-Type Lap Joint (Figure ...) [Details truncated]

IS 6056: Marking Protocols for Jointed Wood Poles

Marking Requirements (Clause 12)

• Marking Location: At 2.5 meters from the base of the pole.

• Marking Information:

  • Pole classification and joint type
  • Timber species abbreviation
  • Year when preservative treatment was applied

• ISI Certification Mark (Clause 12.2):

  • Optional but recommended for quality assurance.
  • Indicates compliance with IS 6056 under the ISI inspection and quality control program.
  • Governed by Indian Standards Institution (Certification Marks) Act.

Additional Considerations

• For poles of non-standard lengths, adopt the circumference of the next larger size as per Table 1 (Clause 4.2).
• Amendments update dimensions and classifications in Table 1.

Marking Summary Table

This marking system ensures traceability, quality control, and conformity with IS 6056 standards for jointed wooden poles.