Methods of test for strength and stability of chairs and stools, Part 1: Strength

IS 5416 Part 2 — Scope & Key Specifications

Scope (Clause 2.0)

• Defines terms and conditions for testing steel as per this standard.
• Applicable to steel testing using specified templates and loading methods.

Key Tables (Clause 7.6.3)

• X and Z are dimensions related to loading points on steel samples.
• Intermediate values can be interpolated graphically.

Loading Setup (Clause 5.1 & 6.2)

• Load applied via a template set at 90° to steel surface.
• Mark loading points using the template (refer Fig. 2 & 3 in the standard).

Summary Diagram: Loading Setup

graph TD
    A[Steel Sample] --> B[Template at 90°]
    B --> C[Mark Loading Point]
    C --> D[Apply Load]

For detailed test procedures, refer to Clauses 5.1, 6.2, and 7.6.3 with the provided tables and figures in IS 5416 Part 2.

IS 5416 Part 2: Definitions & Key Tables

Clause 2.0 - Definitions:
Defines terms specific to the standard for testing seating furniture, e.g., seat load, back load, swivelling base, etc. These ensure uniform understanding for test procedures.

Key Table: Values of X and Z (Clause 7.6.3 & 7.6.4)

• X and Z are critical dimensions for positioning loads during testing.
• Intermediate values can be interpolated graphically.

Load Application (Clause 5.1 & 7.1.1)

• Loads applied: Seat load (A), Back load (B), Seat load for stools (C).
• For swivelling bases, rotate to the most overturning position before tightening.

Summary Diagram: Load Points on Chair

graph LR
    A[Seat Load (A)] --> Chair
    B[Back Load (B)] --> Chair
    C[Seat Load (C) - Stools] --> Chair

Use these definitions and tables to ensure consistent testing and load application per IS 5416 Part 2.

IS 5416 Part 2: Principle of Stability Testing

Principle (Clause 3.1)

• Stability is assessed by simulating overturning forces acting on chairs/stools.
• The test determines if the article overturns under applied forces mimicking real-use conditions.

Key Definitions (Clause 2.1)

• Stability: Ability to resist overturning.

General Test Approach

• Apply a horizontal force or moment at a specified height or point on the chair/stool.
• Measure the maximum force/moment causing overturning.
• Compare with prescribed limits ensuring safety.

Typical Formula for Overturning Moment:

[ M_o = F \times h ]

• M_o: Overturning moment (Nm)
• F: Applied horizontal force (N)
• h: Height of force application point from the ground (m)

Stability Criteria (Generalized)

flowchart LR
    A[Apply Horizontal Force F] --> B[Calculate Overturning Moment M_o = F × h]
    B --> C{Does Chair Overturn?}
    C -- Yes --> D[Fail Stability Test]
    C -- No --> E[Pass Stability Test]

Summary: IS 5416 Part 2 requires simulating overturning forces, calculating moments, and verifying if the chair/stool resists tipping to ensure stability under use.

IS 5416 Part 2: General Requirements for Tests

Key Principles (Clause 3.1)

• Stability is checked by simulating overturning forces.
• The article passes if it does not overturn during testing (Clause 8.1).

Test Pass Criteria (Clause 8.1)

• Article must not overturn.
• Must meet the product specification requirements.

Important Table: Values of X and Z (Clause 7.6.3)

• X and Z represent critical dimensions related to the overturning test setup.
• Intermediate values can be interpolated graphically.

Test Report Requirements (Clause 9.1)

• Article details.
• Whether the article overturned during the test.

Summary Diagram of Overturning Test Concept

flowchart LR
    A[Apply Overturning Force] --> B{Article Stability}
    B -- No Overturn --> C[Pass Test]
    B -- Overturn --> D[Fail Test]

This ensures the article's stability under simulated real-use overturning forces, confirming safety and compliance.

IS 5416 Part 2: Apparatus and Equipment Key Details

1. Support Apparatus (Clause 5.8 & 2.5)

• Mass: Maximum 2.5 kg.
• Used for tests in Clauses 7.6.2 to 7.6.4.
• Dimensions in millimeters.

2. Values of X and Z (Clause 7.6.3 & Table 1)

• Intermediate values can be interpolated graphically.

3. Application

• X and Z values define positional coordinates for apparatus setup in testing.
• Support apparatus ensures consistent loading during tests.

Summary Diagram of Support Apparatus Positioning

graph LR
A[Support Apparatus] --> B(X coordinate)
A --> C(Z coordinate)
B --> D{Angle θ}
C --> D
D -->|0°| E[X=474 mm, Z=614 mm]
D -->|30°| F[X=325 mm, Z=464 mm]
D -->|60°| G[X=194 mm, Z= -]

For detailed apparatus drawings, refer to Fig. 14 in the standard.
All dimensions and mass limits are critical for compliance.

IS 5416 Part 2: Determination of Seat and Back Loading Points

Key Specifications & Procedure

• Loading Point Template (Clause 5.3):

  • Two shaped members pivoted at one end.
  • Designed to sink into upholstery under moderate load.
  • Seat loading arm mass: 20 kg applied at seat loading point.
  • Template members set at 90° angle for positioning.

• Positioning for Chairs (Clause 6.1):

  • Place template on centre line of chair seat, as far rearward as possible.
  • Push back loading portion into backrest, levering seat portion forward.
  • Align template contour with chair shape.
  • Mark seat and back loading points from template.

• Loading Points (Fig. 1 & 2):

  • A: Seat load (chairs)
  • B: Back load (chairs)
  • C: Seat load (stools)
  • All dimensions in mm.

• Swiveling Bases (Clause 7.1.1):

  • Rotate base to position most likely to cause overturning.
  • Tighten before testing.

Summary Table of Loads

Diagram: Loading Point Template Setup

graph LR
    A[Seat Loading Arm (20 kg)]
    B[Back Loading Arm]
    A -- Pivot (90°) --> B
    B --> Upholstery (Backrest)
    A --> Upholstery (Seat)

Note: The template simulates realistic loading by sinking into upholstery, ensuring representative stress points for testing seat and back strength.

IS 5416 Part 2 focuses on stability testing of chairs and stools by simulating overturning forces.

Key Principle (Clause 3.1)

• Stability is assessed by applying overturning forces mimicking real-use conditions.
• The test checks if the chair or stool overturns under these forces.

General Test Setup (from standard practice)

• Apply a horizontal force (F) at a specified height on the chair.
• Measure the overturning moment and compare it with the restoring moment due to weight and geometry.

Typical Formula for Overturning Moment:

[ M_o = F \times h ]

• (F) = applied horizontal force (N)
• (h) = height at which force is applied (m)

Restoring Moment:

[ M_r = W \times b ]

• (W) = weight acting vertically (N)
• (b) = horizontal distance from pivot to center of gravity (m)

Stability Criterion:

• Chair is stable if: [ M_r \geq M_o ]

Typical Test Parameters (from IS 5416 Part 2 and common practice):

graph LR
A[Apply Horizontal Force F at height h] --> B[Generate Overturning Moment M_o = F × h]
C[Weight W acting at distance b] --> D[Generate Restoring Moment M_r = W × b]
B --> E{Is M_r ≥ M_o?}
D --> E
E -- Yes --> F[Chair is Stable]
E -- No --> G[Chair Overturns]

Summary: IS 5416 Part 2 tests chair stability by applying horizontal forces and comparing overturning and restoring moments. Stability depends on geometry, weight, and force application height.

Interpretation of Results - IS 5416 Part 2 (Clause 8 & 7.6.4)

Key points:

• Tests for reclining chairs with footrests follow the procedure in Clause 7.6.3, with discs positioned Z mm from the seat-back intersection.
• Table 1 provides values of X and Z distances for different reclining angles (degrees):

• Note: Intermediate values can be interpolated graphically.

Application:

• Use X and Z to position test discs accurately for load application.
• Compare test results with acceptance criteria (not provided here, refer to full IS 5416 Part 2).
• Ensure correct angle setup for valid interpretation.

Diagram (Conceptual):

graph LR
A[Seat-Back Intersection] -->|X mm| B[Disc Position on Seat Surface]
A -->|Z mm| C[Disc Position on Back Surface]
angle[Reclining Angle] --> A

For detailed acceptance criteria and test load application, consult full IS 5416 Part 2 text.

IS 5416 Part 2 — Test Report Key Points

Test Report Requirements (Clause 9.1)

The test report must include:

• Details of the article tested
• Whether the article overturns during testing

Accuracy of Test Loading (Clause 4.1)

• Loads and forces must be measured with an accuracy of ±5%.

Important Table: Values of X and Z (Clauses 7.6.3 & 7.6.4)

• For reclining chairs with footrests, position three discs at Z mm from the seat-back intersection (Clause 7.6.4).
• Intermediate values can be interpolated graphically.

Summary Diagram of Disc Positioning (Seat-Back Intersection)

graph LR
A[Seat-Back Intersection] --> B[X mm along seat surface]
A --> C[Z mm along back surface]

This table and positioning ensure consistent test application per IS 5416 Part 2.