jointed wood poles for overhead power and telecommunication lines

IS 6056 - Scope: Key Specifications & Tables

Scope (Clause 4.2)

• For poles of intermediate length in Table 1, use the circumference of the next larger pole.
• Final test/analysis values shall be rounded per IS 2-1960 with the same significant figures as specified.

Important Table: Overall Length of Wire Bound Lap Jointed Poles (Clause 11.2.2)

Notes:

• Definitions per IS 707-19 apply.
• Clause 7.5 and 8 references updated as per corrections.

This ensures proper sizing and jointing of poles within the standard's scope.

IS 6056 - Definitions & Key Specifications Summary

1. Definitions (Clause 2.0)

• Definitions in Clauses 2.1, 2.2, and IS 707-19 apply.
• Wood poles are classified by length, circumference, and joint types.

2. Pole Dimensions (Clause 4.2, Table 1)

• Dimensions are grouped by Class 1 to Class 7.
• Minimum circumference at ground line and top of the pole is specified.
• For intermediate lengths, use circumference of next larger pole.

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

3. Timber Species (Appendix A, Clause 7.1)

• Species grouped A, B, C by durability and availability.
• Average weight at 12% moisture content (kg/m³) provided.

Non-durable species are marked with an asterisk.

Summary Diagram: Pole Classification & Dimensions

flowchart TD
    A[Wood Pole] --> B[Class 1 to 7]
    B --> C[Dimensions: Length & Circumference]
    B --> D[Joint Types]
    A --> E[Species Groups A, B, C]
    E --> F[

IS 6056 - Timber Groups & Material Properties for Wood Poles

Timber Groups by Modulus of Rupture (Clause 3.1)

Species & Average Weight (Appendix A excerpt)

Key Notes:

• Moisture content considered is >25% (green condition) for strength classification.
• Species marked with * are non-durable.
• Use IS:1708-1969 for detailed modulus of rupture testing.

graph TD
  A[Timber Groups] --> B[Group A: Very Strong (≥850 kg/cm²)]
  A --> C[Group B: Strong (630-850 kg/cm²)]
  A --> D[Group C: Moderately Strong (450-630 kg/cm²)]
  B --> E[Sal (Shorea robusta)]
  C --> F[Teak (Tectona grandis)]
  D --> G[Chir (Pinus roxburghii)]

This classification aids in selecting appropriate timber species for poles based on mechanical strength and durability.

IS 6056 covers specifications for Steel Tubular Structures. For Load Assumptions and Testing Methods, key points are:

Load Assumptions (Typical as per IS 6056 & related codes)

• Dead Load (DL): Self-weight of tubular members.
• Live Load (LL): As per IS 875 (Part 2) depending on usage.
• Wind Load (WL): As per IS 875 (Part 3), considering shape and exposure.
• Impact Load: Usually 25%-50% of live load for dynamic effects.
• Load Combinations: Follow IS 800 or IS 456 for combined load factors.

Testing Methods

• Tensile Test: To determine yield strength, ultimate strength, and elongation.
• Bend Test: To check ductility and weld quality.
• Hydrostatic Test: For tubular pipes, pressure applied to check leakages.
• Non-Destructive Testing (NDT): Radiography, Ultrasonic Testing for weld defects.

Key Formulas:

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

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

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

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

Typical Table: Allowable Loads (Example)

flowchart LR
    LoadAssumptions --> DeadLoad
    LoadAssumptions --> LiveLoad
    LoadAssumptions --> WindLoad
    LoadAssumptions --> ImpactLoad
    TestingMethods --> TensileTest
    TestingMethods --> BendTest
    TestingMethods --> HydrostaticTest
    TestingMethods

Preservative Treatment Requirements as per IS 6056 & IS 401-1967

1. Preliminary Treatment (Clause 6.1):

• Remove bark completely and dress branches flush (5.1).
• Apply prophylactic treatment per IS 401-1967 ASAP to prevent insect/fungal attack.
• Stack treated components on treated crossers at ≥ 15 cm above ground with proper drainage and cleanliness.

2. Preservative Treatment (Clause 7.1):

• Treat all components to impregnate sapwood completely and as much heartwood of non-durable species as possible.
• Use pressure and preservative types per IS 401-1967 (typically creosote, copper-chrome-arsenic compounds).
• Pressure treatment ensures deep penetration and durability.

3. Timber Species Groups (Appendix A):

• Group A (Non-durable species) require thorough treatment. Examples:
  • Bruguiera spp. (BRU), weight ~893 kg/m³
  • Hopea perviflora (HOP), ~995 kg/m³
  • Kayea assamica (KAY), ~801 kg/m³
• Group B & C species are more durable but may still require treatment depending on use.

Key Table Extract: Selected Non-Durable Species (Group A)

Summary Diagram: Treatment Process Flow

flowchart TD
    A[Prepare Components] --> B[Remove Bark & Dress Branches]
    B --> C[Apply Prophylactic Treatment (IS 401)]
    C --> D[

IS 6056: General Requirements for Jointed Poles

1. Shape and Straightness (Clause 10.3.11)

• Each pole section must be reasonably straight.
• Curvature allowed only in one plane and one direction.
• When assembled, curvatures must be in one plane but opposite directions.
• The sum of maximum deviations (X1 + X2) must not exceed half the mean diameter of the pole.

2. Jointed Pole Dimensions (Clause 11.2.2, Table 11.1)

Key Notes:

• Overlap length ensures structural continuity and strength at joints.
• Poles are assembled so that curvature compensates, maintaining overall straightness.
• Dimensions are critical for mechanical stability and load transfer.

flowchart LR
    A[Top Portion] -->|Overlap| B[Bottom Portion]
    B --> C[Jointed Pole]
    subgraph Curvature Control
        direction TB
        X1[Deviation from top to lower convex side]
        X2[Deviation from ground to upper convex

IS 6056 - Dimensions and Tolerances for Jointed Wood Poles

1. Dimensions (Clause 4.2 & Table 1)

• Poles classified into 7 groups (Class 1 to Class 7).
• Minimum circumference at ground line for lower components varies by class and pole length.
• For example, for a 6 m pole (Class 1):
  • Circumference A: 62 cm
  • Circumference B: 65 cm
  • Circumference C: 72 cm
• For intermediate lengths, use the circumference of the next larger pole size.

2. Joint Sections (Clause 8.1.2)

• Sections jointed must have approximately the same girth at the joint.
• Ensures uniform taper and consistent load class.

3. Joint Lengths (Clause 11.2.2 & Table 11.1)

Summary:

• Use Table 1 for minimum circumferences at ground line.
• Maintain uniform girth at joints.
• Follow minimum overlap lengths

Quality Criteria for Wood Sections (IS 6056)

1. Species Classification & Properties (Appendix A)

• Timber species are grouped (A, B, C) based on durability and availability.
• Key properties include average weight at 12% moisture content (kg/m³).
• Example species:
  • 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 Specifications (Clause 4.2, Table 1)

• Minimum circumference at ground line and top of the upper component are specified for different classes and groups.
• Example for 6m pole length, Group A:
  • Minimum circumference at ground line: 62 cm
  • Minimum circumference at top of upper component: 50 cm

3. General Quality Notes

• Species marked with * are non-durable.
• Moisture content is standardized at 12% for weight and strength values.
• Joint dimensions and species selection must comply with group classification for durability and strength.

flowchart TD
    A[Timber Species] --> B{Group}
    B -->|A| C[High Density & Durability]
    B -->|B| D[Medium Density]
    B -->|C| E[Low Density & Durability]
    C --> F[Higher Min Circumference]
    D --> G[Medium Min Circumference]
    E --> H[Lower Min Circumference]

Summary: Use species from Appendix A per group; check minimum circumferences from Table 1 for pole class and length; ensure moisture content at 12

IS 6056: Types of Jointed Poles and Jointing Details

1. Types of Jointed Poles (Clause 11)

• Butt Jointed Poles (11.4.1):

  • Top & bottom sections placed butt to butt.
  • Fixed by four angle irons (60x60x5 mm).
  • Two opposite angle irons bolted at the joint.

• Wire Bound Lap Jointed Poles (Clause 11.2.2 & Table 11.1):

  • Sections overlap with wire binding.
  • Overlap length varies with pole length.

2. Key Dimensions from Table 11.1 (All in meters)

3. Shape & Straightness (Clause 10.3.11)

• Curvature allowed only in one plane & direction.
• Assembly must have curvatures in opposite directions.
• Sum of max deviations (X1 + X2) ≤ ½ mean diameter.

4. Joint Types Illustrated

• Wire Bound Lap Joint (Fig. 2)
• **Z-Type Lap Joint (Fig.

IS 6056: Marking and Identification of Jointed Wood Poles

Key Specifications (Clause 12)

• Marking Location: At 2.5 m from the bottom end of the pole.

• Marking Details:

  • Class of pole and type of joint
  • Species of timber (by symbol)
  • Year of preservative treatment

• ISI Certification Mark (Clause 12.2):

  • Optional but recommended for quality assurance.
  • Indicates compliance with IS 6056 under ISI's inspection and quality control system.
  • Use governed by Indian Standards Institution (Certification Marks) Act.

Additional Notes

• For poles of intermediate length, use the circumference of the next larger pole as per Table 1 (Clause 4.2).
• Amendments specify updates to dimensions and classifications in Table 1.

Summary Table for Marking

This ensures traceability, quality control, and compliance with IS 6056 standards for jointed wood poles.