Prestressed concrete circular spun poles for overhead power, traction and telecommunication lines
1991 Edition

Overview of Scope and Critical Requirements

• Scope: Pertains to prestressed concrete circular spun poles utilized for electrical distribution, traction, and telecommunication overhead lines.

• Embedding Depth (Clause 6.4 & Table 1):
  Minimum burial depths are specified based on pole length to ensure stability:

• Rounding Protocol: Numerical values should be rounded in accordance with IS 2:1960, preserving the significant figures as specified.

• Related Standards: Refer to Annex A for other Indian Standards important for full compliance.

This ensures poles are embedded at suitable depths corresponding to their length and soil conditions.

Primary References and Numerical Rounding Guidelines

• Rounding Off (No specific clause):
  Adhere to IS 2:1960 for rounding off numerical data, maintaining the original number of significant digits.

• Referenced Codes (Clause 2.1):
  Annex A enumerates Indian Standards that are integral to IS 13158's application.

• Terminology (Clause 3.0):
  Definitions and terms are provided to standardize interpretation.

• Minimum Embedment Depth (Clause 6.4 & Table 1):
  Embedment depth varies according to pole length and ground conditions.

Summary:
Embedment depths should be chosen from Table 1 based on pole length, with rounding following IS 2:1960. Annex A provides supplementary standards.

Key Definitions and Rounding Conventions

Clause 3.0 of the standard provides the terminology essential for consistent comprehension:

• Rounding Instructions (per IS 2:1960):

  • Final numerical results, such as test data or calculations, must be rounded according to the rules in IS 2:1960.
  • The number of significant digits retained should match that specified in the standard.

• Referenced Standards:

  • Annex A lists Indian Standards necessary for applying IS 13158.

• Additional Notes:

  • This section does not include formulas or tables.
  • Definitions help maintain uniformity in terms concerning materials, structural elements, and testing methods.

Rounding Example per IS 2:1960

For specific formulas or further definitions, refer to other clauses.

Specifications for Length, Diameter, and Verticality

1. Length and Diameter Tolerance (Clause 4.2)

• Overall length tolerance: ±15 mm
• Outside diameter tolerance: +4 mm (negative tolerance not explicitly stated)
• Uprightness tolerance: 0.5% of pole length unless otherwise noted

2. Embedment Depth (Clause 6.4, Table 1)

3. Transverse Load Position (Clause 3.7)

• Maximum transverse loads act at 600 mm below the pole's upper end.

4. Quality Control (Clause 9.2.1)

• Poles must be examined for length, cross-sectional dimensions, and verticality.
• Number of defective poles must not exceed acceptance limits provided in Table 2.

Diagrammatic Summary:

graph TD
    Length[Overall Length] --> TolLength[±15 mm Tolerance]
    Length --> Uprightness[≤ 0.5% Uprightness]
    Length --> Diameter[+4 mm Diameter Tolerance]
    Length --> Embedment[Embedment Depth per Table 1]

Material Criteria and Stress Limits

1. Allowable Design Stresses (Clause 6.5.4):

• Concrete compressive stress under average permanent loads: per IS 1343:1980.
• Concrete flexural tensile stress (average permanent load): [ f_{ct,perm} = 3.0 ; \text{N/mm}^2 ]
• High tensile steel stresses: governed by IS 1343:1980.

2. Numerical Rounding:

• Follow IS 2:1960 for rounding numerical values.
• Maintain the same number of significant digits as indicated.

3. Reference Documents (Clause 2.1):

• IS 1343:1980 for prestressed concrete stresses.
• IS 2:1960 for rounding rules.
• Additional relevant Indian Standards listed in Annex A.

Permissible Stress Summary Table

For comprehensive material properties, refer to IS 1343:1980 and related codes in Annex A.

Core Design Guidelines and Calculations

1. Minimum Embedment Depth (Clause 6.4)

Embedment depth varies with pole length as follows:

Note: Actual embedment may vary depending on soil and site conditions.

2. Transverse Load at Initial Cracking (Clause 3.4)

• The transverse force causing first crack must be at least equal to the working load to ensure safety against cracking under service conditions.

3. Rounding Practices

• All computed or measured values must be rounded as per IS 2:1960.
• The number of significant digits retained should correspond to those in the standard.

4. References

• Consult Indian Standards listed in Annex A for supplementary design guidance.

Summary Flowchart

flowchart LR
    A[Pole Length] --> B{Length Range}
    B -->|6-7 m| C[Embed 1.20 m]
    B -->|7.5-9 m| D[Embed 1.50 m]
    B -->|9.5-11 m| E[Embed 1.80 m]
    B -->|11.5-13 m| F[Embed 2.00 m]
    B -->|...| G[Corresponding Embedment]

Manufacturing Guidelines for Prestressed Concrete Spun Poles

1. Mould Specifications (Clause 7.1.1)

• Construct moulds from steel to ensure rigidity and prevent deformation.
• Interior surfaces must be smooth to avoid grout leakage during spinning.
• End plates require accurately drilled holes for high tensile wires, produced via jigs to guarantee interchangeability.
• End plates must withstand forces generated during prestressing wire tension variation.

2. In-Process Testing (Clauses 7.6 & 8.1)

• Conduct concrete tests during manufacturing to verify compliance with quality requirements.

3. Sampling and Acceptance (Clause 9.1.3, Table 2)

• Poles failing at first crack test but with cracks closing after load removal are acceptable.

4. Rounding of Test Results

• Final measurements must be rounded per IS 2:1960, preserving the number of significant figures.

Manufacturing Flow

flowchart TD
    A[Mould Preparation] --> B[Spinning Operation]
    B --> C[Concrete Quality Testing]
    C --> D[Sampling per Table 2]
    D --> E{Acceptance Criteria}
    E -->|Pass| F[Dispatch Finished Poles]
    E -->|Fail| G[Rework or Reject]

Testing Protocols for Quality Assurance

1. Sampling and Number of Tests (Clause 9.1.3 & Table 2)

• Poles tested up to first crack stage but with crack closure after load removal are acceptable.

2. Transverse Strength Testing (Clause 8.2)

• Performed according to IS 2905:1989.
• Failure criteria:
  • Cracks wider than 0.1 mm before first crack design load indicate failure.
  • Ultimate transverse load less than design ultimate load also causes failure.

3. Rounding Off Test Results (Clause 9.2)

• Round final test values as specified in IS 2:1960.
• Maintain the significant digits as required.

Testing Workflow

flowchart TD
    A[Select Lot Size] --> B[Determine Sample & Acceptance Numbers]
    B --> C[Perform Dimensional and Strength Tests]
    C --> D{Evaluate Test Results}
    D -->|Pass| E[Accept Lot]
    D -->|Fail| F[Reject Lot]

Guidelines for Sampling and Inspection

1. Sampling Scheme (Clause 9.1.3 & Table 2)

• Poles examined up to first crack are acceptable if cracks close post load removal.

2. Testing and Conformity (Clause 9.2)

• Test results must meet acceptance numbers for dimensional and strength parameters.
• Final values rounded according to IS 2:1960, preserving specified decimal places.

Summary

• Sample sizes vary by lot size.
• Acceptance numbers differ by test type.
• Rounding follows IS 2:1960 standards.

flowchart TD
    A[Determine Lot Size] --> B{Select Sample Size}
    B -->|≤100| C[Sample 10]
    B -->|101-200| D[Sample 15]
    B -->|201-300| E[Sample 20]
    B -->|301-500| F[Sample 30]
    C --> G[Check Dimensional Defects ≤ 1]
    C --> H[Check First Crack Strength Defects ≤ 2]
    C --> I[Check Ultimate Strength Defects ≤ 1]
    %% similar for other samples

Marking Requirements and Packaging Guidelines

Marking (Clause 10.1)

Poles must be marked clearly and permanently at a visible location (post-installation) with:

• Month and year of manufacture
• Manufacturer’s name or registered trademark
• Unique serial number of the pole
• Center of gravity location indicated as "C.G."

Sampling and Acceptance (Clause 9.1.3 & Table 2)

• Poles tested up to first crack and exhibiting crack closure are acceptable.

Rounding Practices

• Test results must be rounded as per IS 2:1960, retaining the original number of significant digits.

This ensures traceability, quality verification, and compliance throughout production and testing.