Code of practice for use of fixing devices in walls, ceilings and floors of solid construction

IS 1946: Scope - Key Points & Formulas

• Scope: IS 1946 covers specifications related to expansion plugs and screws used in structural applications.
• Units: Metric system is adopted (Clause 0.6).
• Rounding off: Final test values must be rounded as per IS:2-1960, retaining the same number of significant figures as specified (Clause 0.7).

Important Formula

• Plug length calculation (Example from Clause 1.3):

  [ p = 0.35 \times d \times l ]

  where,

  • ( p ) = load capacity (kN or kgf)
  • ( d ) = diameter of plug (mm)
  • ( l ) = length of plug (mm)

• Example: For ( p = 30 ), solving ( 30 = 0.35 \times d \times l ) gives ( l = 86 ) mm for a given ( d ).

Plug Size Selection (Clause 6.85)

• For a plug length limited to 50 mm, diameter ( d = 6.85 ) mm, nearest standard size is 7 mm diameter × 50 mm length.

Summary

• Use metric units.
• Round off values as per IS:2.
• Use the formula ( p = 0.35 d l ) for plug load capacity.
• Limit plug length to 50 mm; select nearest diameter (e.g., 7 mm).

flowchart LR
    A[Load Capacity, p] --> B[Plug Diameter, d]
    A --> C[Plug Length, l]
    B & C --> D[Calculate p = 0.35 × d × l]
    D --> E[Select Plug Size]

This covers the scope essentials for IS 1946 regarding expansion plugs and screws.

IS 1946: General Requirements and Definitions

• Scope (Clause 0.8):
  Focuses on design, material quality, and fixing device application. Does not cover all contract provisions.

• Rounding Off (Clause 0.7):
  Values must be rounded per IS:2-1960 rules:

  • Retain the same number of significant figures as the specified value.
  • Ensures consistency in test results and calculations.

• Requirements (Clauses 3.2 & 4.2):
  Define minimum criteria for materials, design, and workmanship to ensure safety and performance.

Key Notes:

Summary Diagram:

graph TD
  A[IS 1946 General Requirements]
  A --> B[Design Requirements]
  A --> C[Material Quality]
  A --> D[Fixing Devices Application]
  A --> E[Rounding Off per IS:2-1960]

This ensures uniformity and reliability in structural fixing device design and application.

IS 1946: Expansion Wall Plugs – Key Specifications

Materials & Construction (Clause 3.2.2 & 3.2.1)

• Materials: Jute fibre, white bronze, lead alloy, or other suitable materials based on use.
• Properties:
  • Resilient to side compression in drilled holes.
  • Termite-proof and reasonably damp-proof.
  • Allows manual tightening and screw reinsertion.
  • Must develop minimum specified strength with a safety factor ≥ 4.
  • No cracking or masonry disturbance on installation.

Screws for Expansion Wall Plugs (Clause 3.3)

• Use Wood screws (IS:451-1953) or Coach screws (IS:1120-1957).
• Avoid brass screws with white bronze plugs.
• Use cadmium-plated screws for white bronze plugs.
• Use stainless steel screws for lead alloy plugs.

Plug & Screw Size Table (Summary)

Summary Diagram: Plug-Screw Compatibility

graph TD
  A[

IS 1946 - Expansion Shells: Key Design & Application Details

1. Basic Principle (Clause 4.1)

• Expansion shells are metallic segmented assemblies that expand radially when a bolt is tightened.
• They grip firmly against the hole sides in hard materials (e.g., concrete).
• No grouting required.
• Two types:
  • Loose-bolt type: Bolt fitted independently; nut inside shell.
  • Bolt-projecting type: Bolt incorporated; threaded end projects for nut.

2. Components & Action

• Segments held by a ferrule at one end.
• Bolt passes through ferrule center.
• Nut or bolt head is conical to ensure smooth, even segment expansion.

3. Bolt Sizes (Clause 4.5.1)

• Bolt diameter = bolt shank diameter.
• Bolts made of mild steel (Clause 4.3).
• Corresponding nuts (conical or normal) ensure smooth operation.

4. Typical Application Dimensions

• Hole diameter slightly larger than bolt diameter for shell insertion.
• Excess depth (Y) accommodated by collars (see Fig. 4 & 5).

Summary Diagram

graph TD
    A[Expansion Shell Segments] -->|Held by| B[Ferrule]
    B --> C[Bolt (through center)]
    C --> D[Nut (conical shape)]
    D --> E[Segments expand radially]
    E --> F[Grips hole sides in concrete]

Note: For detailed sizing and installation, refer to respective figures (4 & 5) in IS 1946.

IS 1946: Caulked-in Anchor Devices Key Points

Types (Clause 5.1)

• Bolt-anchor type
• Expansion tamp type

Both must achieve minimum anchorage strength per Clause 5.4.4 (not detailed here).

Size Selection (Clause 5.4.5)

• Size of bolt-anchor devices depends on masonry strength.
• Choose bolt size to match masonry load capacity.

Fixing Method (Clause 4.6)

• Mark hole centers accurately.
• Drill hole diameter so expansion shell fits snugly.
• Hole depth must fully accommodate shell and ferrule; increase depth for weak masonry.
• Insert shell with bolt (bolt-projecting type) or without bolt (loose-bolt type).
• Fill excess hole depth with collars if needed.
• Fix fixture, then tighten bolt or nut to achieve anchorage.

Bolts (Clause 5.2)

• Use normal hexagonal or square-headed bolts.
• Bolt size must match bolt-anchor hole or expansion tamp thread.

Typical Design Considerations:

flowchart LR
    A[Mark hole centres] --> B[Drill hole to fit shell]
    B --> C{Masonry strength?}
    C -->|Weak| D[Increase hole depth + add collars]
    C -->|Strong| E[Standard hole depth]
    D & E --> F[Insert shell (with/without bolt)]
    F --> G[Fix fixture]
    G --> H[Tighten bolt/nut]
    H --> I[Achieve anchorage strength]

For detailed anchorage strength values and bolt sizing, refer to IS 1946 Clause 5.4.4 and relevant tables.

IS 1946: Built-in Devices & Expansion Wall Plugs — Key Points

Built-in Devices (Clause 2.2 & 6.1)

• Embedded in masonry/concrete during construction.
• Types:
  • Metallic socket with threads for bolt fixtures.
  • Soft material blocks for screw fixtures.
  • Wedge-shaped wooden plugs for nail/screw fixing.

Expansion Wall Plugs (Clause 6.1, 6.85)

• Plug length generally limited to 50 mm.
• Diameter example: For 50 mm length, plug diameter ≈ 7 mm.
• Plug size example: 7 mm diameter × 50 mm length is recommended.

Caulked-in Devices (Clause 5.1)

• Two types:
  • Bolt-anchor.
  • Expansion tamp.
• Must satisfy minimum anchorage strength per Clause 5.4.4.

Summary Table: Typical Plug Sizes

Design Notes:

• Ensure embedment depth matches plug length for adequate anchorage.
• Use metallic threaded sockets for bolt fixtures requiring higher strength.
• Soft plugs are suitable for light fixtures with screws/nails.

flowchart TD
    A[Construction Phase] --> B[Embed Built-in Device]
    B --> C{Type of Device}
    C -->|Metallic Thread| D[Use Bolt Fixture]
    C -->|Soft Material| E[Use Screw Fixture]
    C -->|Wooden Plug| F[Use Nails/Screws]

For detailed anchorage strength and installation, refer to Clause 5.4.4 and Table A-2 (Clause 6.85) in IS 1946.

IS 1946 - Selection of Size and Length of Fixing Devices

1. Fixing Device Sizes & Lengths (Clause 3.5.7, Table 3.5)

2. Screws for Expansion Wall Plugs (Clause 3.3, Table 3.2)

IS 1946: Methods of Fixing - Key Points & Specifications

1. General Guidance (Clause 0.2)

• Fixing devices like expansion plugs and bolts improve fixture strength and durability.
• Proper tools and devices prevent damage to finishes.
• Special devices resist dampness, chemical attack, and thermal effects.

2. Fixing Procedure (Clause 4.6)

• Select bolt size/length per Clause 4.5.
• Mark hole centers accurately.
• Drill holes with diameter to fit expansion shell snugly.
• Hole depth = length of shell + ferrule; increase depth for weak masonry.
• Insert shell:
  • Bolt-projecting type: shell inserted with bolt.
  • Loose-bolt type: shell inserted without bolt.
• Fill excess hole depth with collars if needed.
• Fix article, then tighten bolt or nut to anchor.

3. Fixing Device Types (Clause 5.5 & 6.4)

• Various devices covered; selection depends on load, masonry type, and environment.
• Caulked-in anchors (Clause 5) provide strong, vibration-resistant fixing.

Typical Fixing Hole Dimensions (Example)

flowchart TD
    A[Mark hole centers] --> B[Drill hole to diameter]
    B --> C{Masonry Type?}
    C -->|Strong| D[Insert shell with/without bolt]
    C -->|Weak| E[Drill deeper hole + fill with collars]
    D --> F[Place fixture]
    E --> F
    F --> G[Tighten bolt/nut for anchorage]

Summary: Accurate hole sizing, proper insertion of expansion shells, and correct tightening ensure durable, damage-free fixings per IS 1946.

IS 1946 Key Formulas & Safety Factors for Load Capacities

1. Safe Direct Load for Expansion Bolt Fixtures (Clause 4.5.5)

• Factor of Safety (FOS):
  • Constant loads: ≥ 5
  • Shock loads: ≥ 10
• Safe load obtained from pull-out tests or manufacturer data.

2. Metallic Socket Fixtures (Clause 6.3.3)

• Ultimate direct load ≥ Breaking load of bolt
• Safe direct load:
  • Constant load = Ultimate load / 5
  • Shock load = Ultimate load / 10
• Safe shear load = 3/4 × Safe direct load
• Safe load calculation same as Clause 4.5.5.

3. Bolt-Anchor in Concrete (Clause 5.4.4)

• Ultimate direct load ≥ Tensile breaking load of bolt.
• Safe direct pull load:
  • Uniform load = Ultimate load / 5
  • Shock load = Ultimate load / 10
• For weak masonry: deeper drilling & multiple anchors recommended.

4. Key Formula (Clause 1.3)

• Load distribution:
  [ p = 0.35 \times d \times l ] where,
  • (p) = load
  • (d) = diameter
  • (l) = length

Summary Table:

flowchart TD
    A[Ultimate Load] --> B[Safe Load]
    B -->|Constant Load| C[Ultimate Load / 5]
    B -->|Shock Load| D[Ultimate Load / 10]
    C --> E[Shear Load = 3/4 × Safe Load]

This ensures conservative design for expansion bolts and metallic fixtures under varying load conditions per IS 1946.

Special Considerations for Weak Masonry (IS 1946)

• Bolt-anchor sizing (Clause 5.4.5, 4.6):

  • Select bolt-anchor size considering masonry strength.
  • Drill deeper holes than normal for weak masonry to increase anchorage length.
  • Use collars to fill excess hole depth above the ferrule for proper fixing.

• Load capacity (Clause 5.4.4):

  • Ultimate direct load = tensile breaking load of bolt (verified by pull-out tests).
  • Safe direct pull load:
    • Uniform load = 1/5 of ultimate load
    • Shock load = 1/10 of ultimate load
  • For weak masonry: increase holding power by deeper drilling and multiple anchors per bolt.

• Shear strength of mortar (Clause 12.5):

  • Mortar shear area = 25 mm × 50 mm = 12.5 cm²
  • Safe shear strength = 1.5 kg/cm²
  • Total strength, F = 4 × 12.5 × 1.5 = 75 kg (use 50 kg for safety)

Summary Table: Safe Pull Loads for Bolt-Anchors

flowchart TD
    A[Select Bolt Size] --> B[Mark Hole Centres]
    B --> C[Drill Hole Deeper for Weak Masonry]
    C --> D[Insert Shell & Bolt]
    D --> E[Fill Excess Depth with Collars]
    E --> F[Tighten Nut/Bolt for Anchorage]
    F --> G[Verify Load Capacity]
    G --> H{Load Type?}
    H -->|Uniform| I[Safe Load = 1/5 Ultimate]
    H -->|Shock| J[Safe Load = 1/10 Ultimate]

This ensures reliable anchorage in weak masonry by accounting for reduced strength and increasing embedment.

IS 1946: Testing and Verification of Anchorage Strength

Key Specifications & Formulas

• Ultimate Load Requirement (Clause 5.4.4):
  The ultimate direct load capacity of a bolt-anchor fixed in standard quality concrete must be ≥ tensile breaking load of the bolt.

• Safe Working Loads:

  • Uniformly applied loads:
    [ P_{safe} = \frac{1}{5} P_{ultimate} ]
  • Shock loads:
    [ P_{safe} = \frac{1}{10} P_{ultimate} ]

• Pull-Out Test:
  Actual pull-out tests must verify anchorage strength unless reliable manufacturer data exists.

• Anchorage Length (Clause 5.4.3):
  The load-bearing caulked length ≈ outside diameter of bolt-anchor crown or expansion tamp.

Installation Notes (Clause 4.6)

• Hole diameter: snug fit for expansion shell.
• Hole depth: enough for shell + ferrule; deeper for weak masonry.
• Excess depth filled with collars.
• Bolt tightened to achieve anchorage.

Summary Table: Anchorage Strength Parameters

flowchart TD
    A[Select bolt size & length] --> B[Mark hole centers]
    B --> C[Drill hole: diameter = shell size]
    C --> D{Is masonry weak?}
    D -- Yes --> E[Drill deeper hole & use multiple anchors]
    D -- No --> F[Drill standard hole depth]
    E --> G[Insert shell + bolt]
    F --> G
    G --> H[Fill excess depth with collars if any]
    H --> I[Tighten bolt/nut to achieve anchorage]
    I --> J[Perform pull-out test or use manufacturer data]
    J --> K[Verify ultimate load ≥ bolt tensile load]

IS 1946 - Appendix A: Key Formulas & Examples for Expansion Plug and Screw Selection

Key Formula (Clause 3.5.2 & Appendix A)

• Load capacity formula: [ p = 0.35 \times d \times l ] Where:
  • ( p ) = load capacity (kN or kgf)
  • ( d ) = diameter of the plug (mm)
  • ( l ) = length of the plug embedded in the wall (mm)

Example Calculation (Clause 1.3)

• Given ( p = 30 ) (load), substitute in formula: [ 30 = 0.35 \times d \times l ]
• For a chosen diameter ( d ), solve for length ( l ): [ l = \frac{30}{0.35 \times d} ]
• Example result: ( l = 86 ) mm (for a specific ( d ))

Typical Examples from Appendix A

• Fig. 10A: Single bracket with distributed load
• Fig. 10B: Single bracket with concentrated load

Selection Guidelines (Clause 3.5.3)

• Choose plug size & length based on:
  • Load magnitude
  • Load type (distributed/concentrated)
  • Wall material strength

Summary Table (Conceptual)

flowchart TD
    A[Load to be supported (p)] --> B[Select plug diameter (d)]
    B --> C[Calculate required embedded length (l) using p=0.35*d*l]
    C --> D[Check plug & screw availability]
    D --> E[Install plug and screw]

Note: Always verify with actual wall conditions and manufacturer's specs for plugs and screws.