Methods of sampling of timber scantlings from depots and their conversion for testing

IS 8720: Scope and Key Specifications

Scope (Clause 2.1)

• Definitions and terms as per IS 707-1976 and IS 2455-1974 apply.
• Covers sampling and selection criteria for timber scantlings.

Selection of Scantlings (Clause 3.3 & 3.4)

• Scantlings must be:
  • Sound and straight-grained
  • Free from decay, center-heart, large knots, twisted grain
  • Free from defects affecting strength

Sampling Notes

• Sample size rationalized per IS 2500 (Part I)-1973 (sampling inspection tables).
• Sampling is based on random methods to ensure representativeness.

Summary Diagram: Scantling Selection Process

flowchart TD
    A[Start: Lot Size] --> B{Lot Size Range}
    B -->|Up to 150| C[Select 20 Scantlings]
    B -->|151 to 300| D[Select 32 Scantlings]
    B -->|301 to 500| E[Select 50 Scantlings]
    C --> F[Check for defects]
    D --> F
    E --> F
    F --> G{Defect Free?}
    G -->|Yes| H[Accept scantling]
    G -->|No| I[Reject scantling]

This ensures quality control and adherence to strength requirements as per IS 8720.

IS 8720 - 1978 (Reaffirmed 2006) References Summary

• Definitions: Use definitions from

  • IS 707:1976+ (Timber Terminology)
  • IS 2455:1974 (Timber Technology)

• Scantlings Quality (Clause 3.4):

  • Must be sound, straight-grained
  • Free from decay, center-heart, large knots, twisted grain, and defects reducing strength

• Sampling & Inspection:

  • Sampling methods per IS 2500 (Part I):1973 for inspection by attributes/defects count
  • Sample size rationalized from 10% to values based on lot size (see IS 2500 tables)

Key Reference Standards for Timber Testing & Sampling

Sample Size Table (from IS 2500 Part I)

This ensures consistent quality control and conformity to timber standards in structural applications.

IS 8720: Selection of Scantlings - Key Points

1. Scantling Size (Clause 3.2)

• Cross-section: ~13 cm x 13 cm
• Length: 1.5 m
• One scantling per log or converted timber, representative of the material.

2. Number of Scantlings to Select (Clause 3.3)

• For lots > 500, follow proportional sampling or IS:4905-1968.
• Additionally, 10% of total scantlings, minimum 20, selected randomly per IS:4905-1968.

Summary:

• Select one 13x13x150 cm scantling per log.
• From the lot, select scantlings as per the table.
• Randomly select 10% (min 20) for testing.

flowchart TD
    A[Individual Logs] --> B[Select 1 Scantling 13x13x150 cm]
    B --> C{Lot Size}
    C -->|Up to 150| D[Select 20 Scantlings]
    C -->|151 to 300| E[Select 32 Scantlings]
    C -->|301 to 500| F[Select 50 Scantlings]
    D & E & F --> G[Randomly select 10% (min 20) for tests]

This ensures representative sampling for quality control per IS 8720.

IS 8720: Storage of Scantlings by Testing Authority

Key Points from Clauses:

• Clause 3.7:
  Scantlings must be packed to prevent moisture ingress and mechanical damage during transport.

• Clause 4.1:

  • Test material ASAP in received condition.
  • If storage is necessary, prevent deterioration using prophylactic treatments per IS 401-1967.

• Clause 3.3 (Selection of Scantlings):
  Number of scantlings depends on lot size:

Additional Notes:

• Use IS 401-1967 for treatment methods (e.g., anti-fungal, anti-termite).
• Mark and convert scantlings per IS 707-1976 and IS 2455-1974.

flowchart TD
    A[Receive Scantlings] --> B{Storage Needed?}
    B -- No --> C[Test Immediately]
    B -- Yes --> D[Apply Prophylactic Treatment (IS 401-1967)]
    D --> E[Store to Prevent Deterioration]
    E --> C

This ensures material integrity before testing.

IS 8720: Marking and Conversion of Scantlings into Test Specimens

Key Specifications:

• Scantling size:
  • Cross-section: 13 cm × 13 cm
  • Length: 1.5 m
• Sampling: One scantling per log/converted timber, representative of the material.

Marking:

• Each scantling shall be marked at one end as per Fig. 1 (typically with ID, source, date).

Conversion into Test Specimens:

• Saw the scantling lengthwise into 4 sticks.
• Each stick size: 6 cm × 6 cm cross-section, same length as scantling (1.5 m).

Notes:

• Test specimens must be taken as soon as possible after receipt to avoid deterioration.
• If storage is needed, follow IS 401:1967 for preservation treatment.

Summary Table:

flowchart LR
    Log/Timber -->|Cut| Scantling[Scantling 13x13 cm, 1.5 m]
    Scantling -->|Mark one end| MarkedScantling
    MarkedScantling -->|Saw lengthwise into 4 sticks| Sticks[4 sticks, each 6x6 cm]
    Sticks -->|Test Specimens| Testing

This ensures uniformity and representativeness in timber testing.

IS 8720: Conditioning of Test Specimens - Key Points

• Conditioning environment (Clause 5.3):

  • Temperature: 27 ± 2°C
  • Relative Humidity (RH): 65 ± 5%
  • Duration: ~1 week
  • Purpose: Minimize moisture variation in wood sticks.

• Specimen preparation (Clause 5.4):

  • After conditioning, sticks are planed to a 5 cm x 5 cm cross-section on four sides before cutting into test specimens.

• Storage and handling (Clause 4.1):

  • Test material should be tested as received or stored with care to prevent deterioration, following IS 401-1967 for prophylactic treatment.

• Specimen selection (Clause 5.5):

  • Follow Appendix A for specimen selection.
  • Specimen lengths per IS 1708-1969.
  • If insufficient material, use uninjured portions from bending tests, considering grain direction and defects.

Summary Table: Conditioning Parameters

flowchart TD
    A[Received Wood Sticks] --> B[Conditioning Chamber]
    B -->|27±2°C, 65±5% RH, ~1 week| C[Planing to 5x5 cm]
    C --> D[Cut into Test Specimens]
    D --> E[Testing as per IS 1708]

This ensures uniform moisture content and standardized specimen size for reliable testing.

IS 8720: Schedule for Selection of Test Specimens

Key Points from Clause 5.5 & Related Clauses:

• Specimen Selection:

  • Specimens are selected from sticks as per Appendix A of IS 8720.
  • Length of test specimens follows IS 1708-1969.
  • If insufficient material, specimens can be taken from uninjured portions of static/impact bending tests.
  • Orientation with respect to growth rings and visible defects must be considered.

• Sample Size (Clause 3.3):

  • Minimum 10% of total scantlings, with a minimum of 20 specimens selected randomly (IS 4905-1968).
  • This is rationalized per IS 2500 (Part I)-1973 sampling inspection tables, which adjust sample size based on lot size.

• Storage & Condition (Clause 4.1):

  • Test material should be tested as soon as possible in received condition.
  • If stored, ensure no deterioration and apply prophylactic treatment per IS 401-1967.

Typical Sample Size Table (Based on IS 2500 Part I):

Note: Exact values depend on inspection level and acceptance quality limit (AQL).

Specimen Length Reference (IS 1708-1969):

flowchart TD
    A[Select Sticks from Lot] --> B[Random Sampling (≥10%, min 20)]
    B --> C[

IS 8720: Method of Selection of Test Specimens for Various Tests

Key Points from IS 8720:

• Sample Size:

  • Select 10% of total scantlings, minimum 20 pieces, randomly from the lot (Clause 3.3).
  • Sampling must follow IS: 4905-1968 for random selection.
  • Sample size rationalized per IS: 2500(Part I)-1973 sampling tables.

• Specimen Selection:

  • Specimens taken from sticks as per Appendix A of IS 8720.
  • Length and dimensions of test specimens follow IS: 1708-1969.
  • If insufficient material, specimens may be taken from uninjured portions of static/impact bending tests.
  • Care to be taken regarding growth ring direction and visible defects.

• Standards Referenced:

  • IS 1708-1969: Methods for testing small clear specimens.
  • IS 2408-1963: Static tests of structural timber sizes.
  • IS 2455-1974: Sampling of model trees/logs.
  • IS 8745-1978: Presentation of timber test data.

Summary Table: Sampling & Specimen Selection

Specimen Length Reference (from IS 1708-1969):

Note: Exact lengths depend on timber species and test method.

flowchart TD
    A[Lot of Timber Scantlings] --> B[Random Sampling (10