Building Design and Erection Using Mixed/Composite Construction - Code of practice

IS 15917: Scope Summary

• Scope Definition: IS 15917 covers design, materials, and construction requirements for formwork systems used in concrete structures.
• References: It incorporates provisions from related Indian Standards (see Annex A), which should be consulted for detailed material tolerances and testing.
• Permissible Tolerances: For steel and masonry components in formwork, refer to relevant IS codes (e.g., IS 2502 for steel tubes, IS 2212 for masonry).
• Rounding Off: Final test or calculation results must be rounded per IS 2:1960 rules, maintaining the same significant figures as specified.

Key Points for Formwork Systems (Clause 7)

Rounding Off Rules (IS 2:1960)

• If the first digit to be discarded is:
  • <5: leave the last retained digit unchanged.
  • ≥5: increase the last retained digit by 1.
• Maintain consistency in significant figures between specified and reported values.

flowchart LR
    A[Design/Analysis] --> B[Calculate Values]
    B --> C{Round Off?}
    C -- Yes --> D[Apply IS 2:1960 Rules]
    C -- No --> E[Use Exact Value]
    D --> F[Final Value]
    E --> F

For detailed design formulas and tables, refer to specific clauses in IS 15917 and referenced IS codes.

IS 15917 - Key Definitions & Specifications

Definitions (Clause 3.17)

• Unit: A building material formed as a simple article with all three dimensions specified, complete in itself but intended to be part of a compound unit or complete building.
  • Examples: Brick, block, tile, etc.

Rounding Off (Clause 4)

• Final test or analysis values must be rounded off per IS 2:1960.
• Retain the same number of significant places as the specified value.

Additional Notes:

• No explicit formulas or tables are provided under "Definitions" in IS 15917.
• For concrete placing (Clause 2.3) and finishing (Clause C-3), practical guidelines are given (e.g., skip discharge height ≤ 0.5 m, power floating within 2-3 hours of casting).

Summary Table: Unit Definition

If you need formulas or tables related to material properties or structural design, please specify the clause or topic.

Modular Co-ordination (IS 15917)

• Basic Module (M):

  • Defined as 100 mm for maximum flexibility.
  • Used as the fundamental unit for dimensional coordination.

• Purpose:

  • Reduce variety in component sizes.
  • Provide flexibility in building component arrangement.

• Modular Dimensions:
  Components and building elements are designed as multiples of M (100 mm) or multimodules (e.g., 2M = 200 mm, 3M = 300 mm, etc.).

• Reference Standard:

  • Modular coordination details and specifications are governed by IS 15916 (for plans, specifications, and detailed modular coordination).

Key Formula:

[ \text{Dimension} = n \times M ] where
( n = ) integer multiplier (1, 2, 3, ...)
( M = 100 \text{ mm (basic module)} )

Typical Modular Sizes Table (Example):

flowchart LR
    A[Basic Module (M = 100 mm)] --> B[Component Size = n × M]
    B --> C{n = 1,2,3,...}
    C --> D[100 mm]
    C --> E[200 mm]
    C --> F[300 mm]
    C --> G[...]

Summary: Use multiples of 100 mm for all dimensional coordination to simplify design and manufacturing as per IS 15917, with detailed guidance in IS 15916.

IS 15917 Key Points: Materials, Plans, and Specifications

1. Materials (Clause 3.17)

• Unit: Building material with all three dimensions specified, e.g., bricks, blocks, tiles.
• Materials must comply with relevant IS standards for quality and dimensions.

2. Plans and Specifications (Clause 4.2)

• Must follow IS 15916:2010 — Code of practice for building design and erection using prefabricated concrete.
• Specifications cover materials, workmanship, tolerances, and equipment.

3. Related IS Codes for Design & Construction

4. Tolerances and Finishes (Clause 6.3)

• Refer to relevant IS codes for permissible tolerances in steel and masonry.

Quick Reference: Unit Weights (from IS 875 Part 1)

Summary Diagram: Material to Construction Flow

flowchart LR
    A[Building Materials (Units)] --> B[Plans & Specifications (IS 15916)]
    B --> C[Design & Construction Codes]
    C --> D[Prefabricated Units & Composite Structures]
    D --> E[Construction & Erection]

Use IS 15916 as primary guide for plans/specs; consult related IS codes for detailed design and execution.

IS 15917 refers modular coordination, architectural treatment, and finishes to IS 15916 for detailed guidelines.

Key Points on Modular Coordination (per IS 15916):

• Basic Module (M) = 100 mm (standard unit)
• Components are sized in multiples of M or multimodules (e.g., 2M = 200 mm, 3M = 300 mm)
• Purpose:
  • Reduce component size variety
  • Enhance design flexibility

Typical Modular Coordination Formula:

• Dimension = n × M
  where n = integer (number of modules)

Architectural Treatment and Finishes:

• Follow IS 15916 for:
  • Surface finishes (plaster, paint, tiles)
  • Treatment of joints and edges
  • Material compatibility and durability

Summary Table (Conceptual):

flowchart TD
    A[Basic Module (M = 100mm)] --> B[Component Sizes = n × M]
    B --> C[Reduced Variety of Sizes]
    B --> D[Flexible Building Layout]
    E[Architectural Treatment] --> F[Surface Finishes]
    E --> G[Joints & Edges]
    E --> H[Material Compatibility]
    style A fill:#f9f,stroke:#333,stroke-width:2px
    style E fill:#bbf,stroke:#333,stroke-width:2px

For full details, refer to IS 15916 as IS 15917 defers to it for these aspects.

IS 15917: Dimensions and Tolerances - Key Points

• Preferred Dimensions & Casting Tolerances
  Refer to IS 15916 for standard dimensions and permissible casting tolerances of precast concrete elements. This ensures uniformity and interchangeability.

• Permissible Tolerances for Materials

  • Steel & Masonry: Follow relevant Indian Standards (e.g., IS 456 for concrete, IS 800 for steel).
  • Timber: Tolerances as per SP 7 (Part 6/Sec 3A).

• Increments (Clause 3.6)

  • Defined as the difference between homologous dimensions of successive sizes, crucial for modular coordination.

Typical Tolerance Ranges (Reference from IS 15916 & related codes)

Note: Exact values depend on element type and function; always verify with IS 15916 tables.

Conceptual Diagram: Dimensional Tolerance in Precast Elements

graph LR
A[Nominal Dimension] --> B[Permissible Tolerance (+/-)]
B --> C[Actual Dimension]
C --> D[Acceptable Range]

Summary: Use IS 15916 for dimensional standards and tolerances of precast concrete, SP 7 for timber, and relevant IS codes for steel/masonry to ensure quality and fitment in construction.

IS 15917 - Formwork Systems Key Points

1. Tunnel Form (Clause 7.1)

• Casts walls and slabs together in a single concrete pour.
• Components: Steel.
• Enables rapid construction and early stripping with accelerated curing.
• Facade walls are precast or block masonry for easy removal.

2. Aluminium Formwork (Clause 7.3)

• Made entirely of aluminium (lightweight & rust-free).
• Suitable for walls, slabs, bay windows, stairs, hoods.
• Easy manual handling, reducing heavy equipment use.

3. Large Panel Shuttering System (Clause 7.4)

• Vertical load members: Steel.
• Horizontal members: Plywood sandwiched between wooden beams (web flange).
• Designed to carry actual construction loads for speed and quality.

Typical Design Considerations for Formwork Systems:

• Load calculations: Dead load + live load + concrete pressure.
• Permissible deflection: Usually L/600 to L/1000 of span.
• Safety factors: As per IS 456 and IS 15916 for formwork loads.

Example: Formwork Pressure on Vertical Walls (IS 456)

[ P = 0.6 f_c' \quad \text{(kN/m}^2\text{)} \quad \text{or} \quad P = \gamma_c \times h ]

• (P) = pressure on formwork
• (f_c') = concrete compressive strength
• (\gamma_c) = unit weight of concrete (~24 kN/m³)
• (h) = height of fresh concrete

graph TD
A[Formwork Systems] --> B[Tunnel Form]
A --> C[Aluminium Formwork]
A --> D[Large Panel Shuttering]
B --> E[Steel Components]
C --> F[Lightweight Aluminium]
D --> G[Steel Verticals]
D --> H[Plywood + Wood Horizontals]

For detailed load tables and tolerances, refer to IS 15917 clauses and related IS codes (IS 456, IS 15916).

IS 15917: System and Structural Schemes - Key Points

1. System Flexibility & Constraints (Clause 8.1)

• Multiple structural schemes can be developed using the same set of components.
• Each system has varying degrees of flexibility.
• All systems must maintain order and discipline in assembly.

2. New Systems Approval (Clause 7.5)

• Any new or alternative system requires prior approval from the Authority before use.

3. Design Considerations

• Systems must accommodate services installations (piping, wiring, accessories).
• Design should ensure compatibility with formwork and structural elements.

4. Tolerances (Clause 6.3)

• Refer to relevant Indian Standards for permissible tolerances in steel and masonry.

Typical Structural Scheme Components (General Guidance)

Conceptual Diagram of Structural Scheme

graph TD
  A[Columns] --> B[Beams]
  B --> C[Slabs]
  C --> D[Services (Piping, Wiring)]
  A --> E[Foundations]
  B --> F[Joints & Connections]
  style A fill:#f9f,stroke:#333,stroke-width:2px
  style B fill:#bbf,stroke:#333,stroke-width:2px
  style C fill:#bfb,stroke:#333,stroke-width:2px
  style D fill:#ffb,stroke:#333,stroke-width:2px
  style E fill:#fbb,stroke:#333,stroke-width:2px
  style F fill:#fbf,stroke:#333,stroke-width:2px

Summary: IS 15917 encourages flexibility in system schemes but mandates discipline, approval for new systems, and adherence to tolerances per relevant IS codes. Design must integrate all structural and service components harmoniously.

IS 15917 - Design Considerations: Key References & Specifications

1. Composite Structures & Precast Units

• Use IS 3935 for composite construction of prefabricated units with cast-in-situ concrete.
• For precast reinforced/prestressed concrete triangulated trusses, refer IS 3201.
• For floors/roofs with precast units, refer:
  • IS 6332 (shell units)
  • IS 10297 (ribbed/cored slabs)
  • IS 10505 (waffle units)
  • IS 13994, IS 14142, IS 14215, IS 14242 (various precast units)
• Large panel prefabricates: IS 11447.
• Floors/roofs with joists & filler blocks: IS 6061 (Parts 1 & 2).

2. Loads & Safety

• Design loads (dead, imposed, wind, snow): IS 875 (Parts 1-5).
• Earthquake resistance: IS 1893 (Part 1 & 2).
• Safety against progressive collapse & joint design: IS 15916.

3. Formwork & Construction Practice

• Formwork system considerations (Clause 8.2) include:
  • Efficient space use, simple walling, limited component sizes, standardized services, ease of erection.
• Component testing & sampling: per IS 15916.

Summary Table of Key IS Codes for Design Considerations

IS 15917 - Manufacture, Storage, Transport, and Erection of Precast Concrete Elements

Key Points & References:

• Manufacture, Storage, Transport, Erection must comply with IS 15916:2010 (Code of Practice for Precast Concrete).
• For composite construction (prefab + cast-in-situ), refer IS 3935.
• For precast reinforced/prestressed trusses, refer IS 3201.
• For floors/roofs with various precast units, refer:
  • IS 6332, IS 10297, IS 10505, IS 13994, IS 14142, IS 14215, IS 14242.
• For large panel prefabricates: IS 11447.
• For floors/roofs with joists & filler blocks: IS 6061 (Parts 1 & 2).
• Equipment used must comply with IS 15916.

Typical Specifications Summary:

Important Design Load References (for transport/erection):

General Formula for Lifting/Handling Stress Check:

[ \sigma = \frac{P}{A} + \frac{M \times c}{I} ]

Where:

• (\sigma) = Stress in the element during lifting
• (P) = Axial load (lifting force)
• (A) = Cross-sectional area
• (M) = Bending moment due to lifting points
• (c) = Distance from neutral

IS 15917: Handling & Placement of Reinforcement - Key Points

1. Reinforcement Support & Stability (Clause 1.4)

• Use plastic stools, loops, or preformed mesh chairs to support reinforcement.
• Avoid plastic channels as they may cause cracking.
• Chairs must be robust to resist displacement during concreting.
• Check reinforcement after fixing, especially around openings and for any additional bars.
• Be cautious of impacts from concrete pumping pipes which can displace reinforcement.

2. Concrete Placement on Decking (Clause 2.1 & Annex B)

• Place concrete to minimize decking deformation, especially for spans > 3 m.
• When concreting parallel to decking ribs:
  • Start over supports → mid-span → end supports.
• When concreting perpendicular to ribs:
  • Start at edges supported by underlapping sheets.
• Use vibrating beam or immersion needle vibrator for compaction.
• Avoid hand tamping; use needle vibrators for deep decking or partially encased beams.

3. Additional References (Clause 12.4 & Annex A)

• For composite and precast construction, refer to:
  • IS 3935 (Composite Construction)
  • IS 3201 (Precast Trusses)
  • IS 6332, IS 10297, IS 10505 (Precast Floors & Roofs)
  • IS 15916 (Equipment for precast concrete)

Summary Table: Reinforcement Handling & Concrete Placement

flowchart TD
    A[Fix Reinforcement] --> B[Support with Chairs]
    B --> C{Check for Displacement?}
    C -- Yes --> D[Adjust & Recheck]
    C -- No --> E[Start Concrete Placement]
    E --> F{Direction of Pour?}
    F -- Parallel --> G

IS 15917 - Decking and Concreting Practices: Key Points

1. Decking Fixing (Annex B - Clause 12.2)

• Fix decking sheets on top of supporting structure.
• Fixings through troughs at:
  • 300 mm centers along end supports (every trough).
  • 600 mm centers along internal supports (alternate troughs).
• Minimum 2 fixings per sheet per permanent support.
• Fixings not allowed on temporary supports.
• Fixings + welded studs provide lateral restraint during construction.

2. Concreting on Decking (Clause 12.3 & Annex C)

• Follow Annex C for concreting practices.
• Concrete placing must ensure proper compaction and bonding with decking.
• Refer to IS 3935 for composite construction design.

3. References for Design & Construction of Composite Floors/Roofs:

Summary Table: Decking Fixing Spacing

flowchart TD
    A[Receiving & Storing Decking] --> B[Fix Decking Sheets]
    B --> C{Fixing Centers}
    C -->|End Supports| D[300 mm centers, every trough]
    C -->|Internal Supports| E[600 mm centers, alternate troughs]
    B --> F[Minimum 2 fixings per sheet per support]
    F --> G[Lateral restraint by fixings & welded studs]
    G --> H[Concrete Placing (Annex C)]
    H --> I[

IS 15917 - List of Referred Indian Standards

IS 15917 references several key IS codes for design, materials, and construction practices related to prefabricated concrete structures:

Key Notes:

• Materials used in prefabrication must conform to relevant IS standards (Clause 4.1.1).
• For composite structures combining precast and cast-in-situ concrete, refer to IS 3935.
• For precast trusses and purlins, IS 3201 is applicable.
• Equipment for precast construction must comply with IS 15916.

Summary Diagram of Reference Relationships:

graph LR
A[IS 15917] --> B[IS 3935 Composite Construction]

Key Specifications & Practices for Decking (IS 15917)

Fixing of Decking (Annex B - Clause 12.2)

• Fixings through troughs only:
  • End supports: every ~300 mm (or every trough)
  • Internal supports: every ~600 mm (or alternate troughs)
• Minimum 2 fixings per sheet per permanent support
• No fixings to temporary supports
• Fixings + through-deck welded studs provide lateral restraint during construction

Placement of Decking (Annex C - Clause 12.3)

• Sheets must have minimum 50 mm bearing on steel beams
• Ends of sheets butted with max 5 mm gap (seal with tape or foam if needed)
• Longitudinal edges overlapped to minimize concrete seepage
• Avoid free projections > 600 mm
• Cutting only near columns/obstructions; avoid cutting continuous sheets or at temporary supports
• Dispose scraps promptly; secure partially used bundles

References for Design & Construction

• Composite structures: IS 3935
• Precast trusses: IS 3201
• Floors/roofs with precast units: IS 6332, IS 10297, IS 10505, IS 13994, IS 14142, IS 14215, IS 14242
• Large panel prefabricates: IS 11447
• Joists & filler blocks: IS 6061 (Parts 1 & 2)
• Equipment for precast construction: IS 15916

Summary Table for Fixing Spacing

flowchart TD
    A[Receive Decking Sheets] --> B[Position Sheets on Supports]
    B --> C{Fixing Location?}
    C -->|End Supports| D[Fix at every trough (~300 mm)]
    C -->|Internal Supports| E[Fix at alternate troughs (~600 mm)]
    D --> F[Minimum 

IS 15917: Concreting on Decking (Clause 12.3 & Annex C)

Key Specifications for Concreting on Decking

• Concrete Placement Sequence:

  • For decking spans > 3 m, concrete is placed:
    • First over supports (continuous decking),
    • Then mid-span,
    • Finally over end supports.
  • When placing transverse to decking ribs:
    • Start at edges supported by adjacent sheet underlaps to keep seams closed.

• Compaction:

  • Use vibrating beam or immersion needle vibrator.
  • Hand tamping is not recommended.
  • Needle vibrator essential for slim floors with deep decking or partially encased beams.

• Fixing Decking Sheets:

  • Fix through troughs at:
    • ~300 mm centers on end supports,
    • ~600 mm centers on internal supports.
  • Minimum 2 fixings per sheet per permanent support.
  • Fixings provide lateral restraint during construction.

Related IS Codes for Composite & Precast Floors (Clause 12.4)

Summary Diagram: Concrete Placement Sequence on Decking

flowchart LR
    A[Start Concrete Placement] --> B{Direction of Placement}
    B -->|Parallel to ribs| C[Place at Supports]
    C --> D[Place at Mid-span]
    D --> E[Place at End Supports]
    B -->|Perpendicular to ribs| F[Place at Edge with Underlap]
    F --> G[Continue Inward]

Note: For detailed mix design, reinforcement, and structural checks, refer to IS 15917 Annex C and related IS codes above.