Methods of static tests of timber in structural sizes

IS 2408: Scope Summary

• Purpose: Covers methods of static tests for structural timber sizes to determine strength properties.
• Exclusions:
  • Does not cover sampling, selection, or data analysis procedures (to be covered in a separate standard).
  • Does not include contract provisions.

Key Points from IS 2408

Appendices (for formulas and data recording)

• Appendix B: Sample data sheet template for recording test results.
• Appendix C: Formulas to compute mechanical properties such as bending strength, modulus of elasticity, etc.

Typical Formulas (from Appendix C, general knowledge)

Where:

• (P) = Load at failure or at specified point
• (L) = Span length
• (b) = Width of specimen
• (d) = Depth of specimen
• (\delta) = Deflection at load (P)

This standard is essential for uniform testing procedures but relies on complementary standards for sampling and data analysis.

IS 2408: Definitions & Data Recording for Timber Strength Testing

Key Points from IS 2408:

• Recording of Data:
  All test data must be recorded on the sample data sheet as per Appendix B.

• Computation of Properties:
  Mechanical properties (e.g., strength, modulus of elasticity) are calculated using formulas in Appendix C.

• Purpose:
  Collecting strength data on structural timber sizes ensures reliability and standardization in design.

Typical Formulas (Appendix C) for Strength Properties:

• P = Load at failure (N)
• A = Cross-sectional area (mm²)
• Δσ, Δε = Stress and strain increments

Summary:

• Use Appendix B for data sheets.
• Use Appendix C for strength & modulus calculations.
• Applies to compression parallel and perpendicular to grain.

flowchart TD
    A[Start: Timber Test] --> B[Record Data in Appendix B Sheet]
    B --> C[Calculate Properties using Appendix C Formulas]
    C --> D{Type of Test?}
    D -->|Compression Parallel| E[Use \( f_c = P/A \)]
    D -->|Compression Perpendicular| F[Use \( f_{c\perp} = P/A \)]
    E --> G[Evaluate Strength]
    F --> G
    G --> H[Complete Report]

This ensures standardized data collection and calculation for timber strength per IS 2408.

IS 2408: Classes of Tests

The standard divides tests into two classes:

1. Major Tests (Clause 3.1.1)

• Conducted on full-sized structural members.
• Tests include:
  • Structural bending
  • Compression parallel to grain
  • Compression perpendicular to grain

2. Minor Tests (Clause 3.1.2)

• Performed on small-clear-specimens from matched portions or undamaged areas of material used in major tests.
• Include:
  • Static bending
  • Compression parallel & perpendicular to grain
  • Indentation
  • Shear
• Must be done simultaneously with major tests to avoid condition changes.
• Also include specific gravity and moisture content determinations.
• Follow IS 1708 (Part I)-1960 for methods on small clear specimens.

Summary Table

flowchart TD
    A[Tests on Timber] --> B[Major Tests]
    A --> C[Minor Tests]
    B --> B1[Full-sized specimens]
    B --> B2[Bending, Compression (parallel & perpendicular)]
    C --> C1[Small-clear specimens]
    C --> C2[Static Bending, Compression, Indentation, Shear]
    C --> C3[Specific Gravity & Moisture Content]

This classification ensures comprehensive evaluation of timber's structural and material properties.

IS 2408: General Requirements - Key Formulas, Tables, and Specifications

• Data Recording:
  All test data must be recorded on the sample data sheet as per Appendix B.

• Property Calculations:
  Mechanical properties (like strength, modulus of elasticity) are calculated using formulas provided in Appendix C.

• Key Notes:

  • This applies to all tests: compression parallel/perpendicular to grain, bending, tension, etc.
  • Ensures uniformity and comparability of test results.
  • Appendix B standardizes data entry, while Appendix C provides standard formulas such as:

• Purpose:
  To maintain consistency in data recording and ensure accurate computation of wood properties for structural design.

flowchart LR
    A[Sample Preparation] --> B[Testing]
    B --> C[Record Data (Appendix B)]
    C --> D[Calculate Properties (Appendix C)]
    D --> E[Report Results]

For detailed formulas and data sheets, refer directly to Appendices B and C of IS 2408.

IS 2408: Static Bending Tests – Key Formulas & Specifications

Specimen Dimensions (Clause 5.1)

• Length: ≥ 350 cm
• Depth: ≥ 20 cm
• Breadth: ≥ 15 cm
• Measure width & depth every 15 cm over middle third, nearest mm.

Ring Width (Clause 4.9)

• Measure average ring width radially in peripheral, intermediate, and core zones of cross-section.

Rate of Loading (Clause 5.4)

• Load applied continuously to produce strain rate of 0.0015 cm/cm/min at outer fibre.
• Head speed (N) formulas:

For simple beam loading: [ N = Z \times \frac{3L - 4a}{3d \times a} ]

For third-point loading: [ N = \text{(same formula with appropriate } a, L, d \text{ values)} ]

Where:

• (N) = head speed (cm/min)
• (Z) = unit strain rate (0.0015 cm/cm/min)
• (a) = distance from support to nearest load (cm)
• (L) = span length (cm)
• (d) = specimen depth (cm)

Testing Procedure

• Sketch specimen marking defects (Clause 6.2, Fig. 1).
• Use diagrams (Fig. 2A, 2B) for loading methods.
• Record failure mode (Fig. 3).

flowchart LR
    A[Specimen Preparation] --> B[Measure Dimensions & Ring Width]
    B --> C[Apply Load at Rate N]
    C --> D[Record Load & Deflection]
    D --> E[Mark Defects & Failure Mode]

This ensures accurate, repeatable bending test results per IS 2408.

IS 2408: Recording of Data and Computation

• Data Recording:
  Use the Sample Data Sheet from Appendix B to record all observations systematically.

• Property Calculations:
  Calculate properties using formulas provided in Appendix C.

Key Points from IS 2408:

Typical Formulas (Appendix C) for Compression Parallel to Grain:

[ f_c = \frac{P}{A} ]

Where:

• ( f_c ) = compressive strength parallel to grain (N/mm²)
• ( P ) = maximum load (N)
• ( A ) = cross-sectional area (mm²)

Sample Data Sheet (Appendix B) includes:

• Specimen identification
• Dimensions (length, width, thickness)
• Load at failure
• Calculated strength values

flowchart TD
    A[Start: Record specimen data] --> B[Measure dimensions]
    B --> C[Apply load & record max load]
    C --> D[Calculate properties using Appendix C formulas]
    D --> E[Fill sample data sheet (Appendix B)]
    E --> F[Analyze & report results]

This ensures consistent, reliable data recording and computation per IS 2408.

IS 2408: Compression Parallel to Grain - Key Points

Specimen Dimensions (Clause 7.1)

• Cross-section: Minimum 15 cm × 15 cm
• Length: At least 4 times the side of the cross-section (≥ 60 cm)

Testing (Clause 3.1.1)

• Compression parallel to grain is a major test on full-sized structural timber.

Data Recording & Calculation (Clauses 5.8 & 6.8)

• Use Appendix B for sample data sheets.
• Calculate properties using formulas in Appendix C.

Typical Formula for Compression Parallel to Grain Strength (from Appendix C)

[ f_c = \frac{P}{A} ]

Where:

• (f_c) = compressive strength parallel to grain (N/mm²)
• (P) = maximum load at failure (N)
• (A) = cross-sectional area (mm²)

Summary Table (Typical Values from IS 2408)

flowchart TD
    A[Specimen Preparation] --> B[Cross-section ≥ 15x15 cm]
    B --> C[Length ≥ 4 × side]
    C --> D[Apply Load Parallel to Grain]
    D --> E[Record Max Load P]
    E --> F[Calculate Strength: f_c = P/A]

Note: Always refer to the latest IS 2408 for precise values and detailed procedures.

IS 2408: Moisture Content Determination Key Points

• Sample: Take a disc 2.5 cm long from the central portion or failure point of the timber specimen immediately after testing.

• Reference Method: Moisture content (MC) is determined as per Appendix A of IS 1708 (Part 1)-1960.

Moisture Content Calculation Formula (IS 1708)

[ \text{MC} (%) = \frac{W_{\text{wet}} - W_{\text{dry}}}{W_{\text{dry}}} \times 100 ]

• (W_{\text{wet}}) = Weight of the specimen before drying
• (W_{\text{dry}}) = Weight after oven drying (constant weight)

Drying Procedure (per IS 1708)

• Oven dry at 103 ± 2°C until constant weight is achieved (usually 24 hours or more).
• Constant weight means weight change ≤ 0.5% over 2 hours.

Summary Table

This ensures accurate moisture content measurement critical for timber strength evaluation.

IS 2408: Sample Data Sheet & Calculation Formulas

• Sample Data Sheet:
  Refer to Appendix B of IS 2408 for the recommended format to record all observations and test data systematically. It includes fields for specimen details, dimensions, load, deformation, and calculated properties.

• Calculation Formulas:
  Use Appendix C for formulas to compute mechanical properties such as compressive strength, modulus of elasticity, and deformation parameters.

Key Formulas from Appendix C (Typical)

• ( P ) = Load at failure (N)
• ( A ) = Cross-sectional area (mm²)
• ( \Delta \sigma ) = Change in stress
• ( \Delta \epsilon ) = Change in strain

Summary Diagram of Data Flow

flowchart TD
    A[Specimen Preparation] --> B[Load Testing]
    B --> C[Record Data in Sample Data Sheet (Appx B)]
    C --> D[Calculate Properties using Formulas (Appx C)]
    D --> E[Report Mechanical Properties]

Use Appendix B for data recording and Appendix C for property calculations to ensure compliance with IS 2408.

IS 2408 - Key Calculation Formulas & Specifications

The standard emphasizes consistent recording and computation of timber test data using:

• Appendix B: Sample Data Sheet
  Used for systematic recording of test observations (e.g., dimensions, loads).

• Appendix C: Calculation Formulas
  Contains formulas to compute mechanical properties such as:

Common Formulas (from Appendix C)

Where:

• (P) = Load at failure (N)
• (L) = Span length (mm)
• (b) = Width of specimen (mm)
• (d) = Depth of specimen (mm)
• (\delta) = Deflection corresponding to load (P) (mm)
• (A) = Cross-sectional area (mm²)

Notes:

• Use Appendix B for data recording to ensure traceability.
• Apply formulas in Appendix C for compression parallel/perpendicular to grain and bending tests.
• Follow clause references 4.8, 5.8, 6.8, 7.8 for respective test data handling.

flowchart TD
    A[Start Test] --> B[Record Data in Appendix B]
    B --> C[Apply Formulas from Appendix C]
    C --> D[Calculate Mechanical Properties]
    D --> E[Analyze & Report Results]

This approach ensures uniformity and accuracy in timber strength evaluation per IS 2408.