Handbook on Concrete Reinforcement and Detailing

IS SP:34 (S&T)-1987 — Scope: Key Formulas & Tables for Measurement of Bending Dimensions

This standard provides detailed methods for measuring bending dimensions of reinforcement bars in RC structures, essential for accurate bar bending schedules.

1. Measurement of Bending Dimensions of Bars (Clause 5.3, 5.4, 5.5, 5.6)

2. Important Notes

• R = Internal radius of bend (specify if non-standard)
• d = Nominal bar diameter
• B, H, S, E, A, C = Linear dimensions as per sketches
• Hooks/bends must be marked as hook/bend up or hook/bend down.
• Arrows should indicate inside/outside dimensions if ambiguous.

3. Example Formula for a Stirrup (Ref 5.6, Method A):

[ L = 2(A + E) + 4d ]

Where:

• (A, E) = leg lengths
• (d) = bar diameter (bend allowance)

4. Visual Sketches

The standard

IS SP Part 34 - Materials and Properties Summary

1. Physical/Mechanical Properties (Clause 1.1.2, Table 1.1)

• Mild Steel & Medium Tensile Steel bars properties are specified.
• Typical yield strength (0.2% proof stress):
  • Mild Steel: ~250 N/mm²
  • Medium Tensile Steel: ~415 N/mm²
• Ultimate tensile strength and elongation values are also defined.

2. Steel Bar Identification (Tables B-1 & B-2)

• Shape coding system for bars based on bends and anchorage:
  • 1st character: Number/type of bends (0-7, 81-89, 99)
  • 2nd character: Bend radius and direction
  • 3rd & 4th: End anchorage details
• Preferred shapes listed with codes (e.g., 00, 11, 12, 25, 31, 33, 41, 51).

3. Bar Schedule Requirements (Clause 6.3)

• Title block must include:
  • Designer's name, project title, dates, drawing number, bar schedule reference, revision info.
• Bar schedule includes diameter, length, number, shape code, bending dimensions.

4. Hard-Drawn Steel Wire Fabric (Appendix C, Table C-1)

• Mesh sizes, wire diameters, and nominal weights (kg/m²) for square and oblong meshes.

5. High Strength Deformed Steel Bars (Clause 410.0, Table 1.2)

• Yield strength (Fe) grades: Fe 415, Fe 500, Fe 550 with minimum tensile strengths.
• Chemical composition limits for Carbon (C), Sulphur (S), Phosphorus (P).

Quick Reference Table: Steel Bar Properties

Bar Shape Coding Logic (Summary)

graph TD
A[First Character] --> B{Number of bends}
B -->|0|

Key Specifications & Tables for Structural Drawing Detailing (IS SP Part 34):

1. Drawing Sheet Sizes (Clause 3.1, Table 3.1)

• Use one standard sheet size for large projects.
• Preferred trimmed sizes (mm):

2. Information to Show on Drawings (Clause 3.3.5)

• Main dimensions: distances between columns, floor heights, beam/column sizes, slab/wall thickness.
• Sections must be drawn at ≥ 2× scale of plan/elevation.
• Complex joints (e.g., beam-column intersections) detailed at larger scale, e.g., 1:4.

3. Zoning of Drawing Sheets (Clause 3.1G)

• Sheet zoning helps organize drawings by zones for clarity.

Summary:

• Use A0 to A4 sizes for structural drawings.
• Show all main structural dimensions clearly.
• Use scales ≥ 2× for sections, larger for details.
• Divide sheets into zones for clarity.

flowchart TD
    A[Start: Structural Drawing] --> B[Select Sheet Size (A0 to A4)]
    B --> C[Show Main Dimensions]
    C --> D[Draw Sections @ ≥ 2× Scale]
    D --> E{Complex Joint?}
    E -- Yes --> F[Draw at 1:4 Scale]
    E -- No --> G[Proceed]
   

IS SP 34 (S&T)-1987: Key Points on Cutting, Fabrication & Assembly of Reinforcement

1. Cutting (Clause 13.2)

• Use power-operated shears; avoid damage to ribs near cuts.
• Flame or electrode cutting discouraged except for mild steel (may alter heat-treated steel properties).
• Maintain orthogonality of cut sections for welding or sleeve splices.
• Avoid burns on cut surfaces.

2. Fabrication (Clause 13.3.1)

• Bending & Radiusing: Cold operations only; no torch heating.
• Overbending: Required to compensate elastic spring-back (depends on grade & diameter).
• Mandrel Diameter:
  • ≥ minimum bending-rebending test diameter.
  • For anchor hooks, ≥ 5 times bar diameter (5Ø).
• Avoid straightening; prefer accentuated bending if correction needed.
• Visual check for cracks or damage after bending.
• Bending speed depends on steel type & ambient temperature; should be experimentally determined.
• Maintain overall dimensional accuracy for correct placement and concrete cover.

3. Assembly (Clause 13.5)

• Prefabricated reinforcement fixed by ties, couplers, welds, or supports to prevent displacement.
• Consider embedded elements (pipes, recesses) during assembly.
• Reinforcement units limited by transport and lifting capacities.
• Assembly methods include welding, tying, or mechanical couplers.
• Reinforcement factory decides jointing method.

4. Practical Notes

• Use rectilinear bars as much as possible to reduce fabrication cost.
• Cutting, bending, transport, and assembly can consume 4 to 150 man-hours per tonne depending on complexity.
• Store cut & bent bars sorted and labelled near site for easy handling.

Mandrel Diameter Recommendation:

Summary Diagram: Fabrication Process

flowchart TD
    A[Cutting] --> B[Bending & Radiusing]
    B --> C[Visual Inspection]
    C --> D[Assembly & Fixing]
    D

IS SP Part 34: Schedules and Marking of Reinforcement

Key Points from Clauses:

• Clause 3.3.15: Reinforcement details (slabs, beams, columns) should be shown in tabular schedules on working drawings.
• Clause 5.2.2: Schedules must be supplemented with clear diagrams/sketches; no unexplained abbreviations.
• Clause 5.9: Typical schedule format for welded wire fabric in slabs (see Table 5.9).
• Clause 5.5: Measurement methods for bending dimensions of bars (see Table 5.5).

Typical Schedule Table Format (Table 5.9)

Bar Length Measurement Formulas (Table 5.5)

• (H) = Hook allowance, (d) = bar diameter, (S,

Reinforcement for Footings and Columns (IS SP:34)

1. Footing Reinforcement Distribution (Clause 6.5.1)

• One-way footing:
  Reinforcement is uniformly distributed across the full footing width.

• Two-way square footing:
  Reinforcement in each direction is uniformly distributed across full footing width.

• Two-way rectangular footing:

  • Long direction: Uniform across full width.
  • Short direction: Reinforcement concentrated in a central band (width = footing width).
  • Reinforcement in central band:
    [ \text{Central band reinforcement} = \frac{2 \times \text{Total reinforcement in short direction}}{\frac{y}{x} + 1} ] where ( y ) = long side, ( x ) = short side.

2. Typical Reinforcement Details

3. Column Reinforcement (Clause 5.6 & Schedule)

• Main bars:
  • Up to 1st floor: 2#20
  • Up to 2nd floor: #16
  • Above 2nd floor: 2#17
• Ties: #10 bars, spacing as per design (e.g., 200 mm c/c typical).

4. Additional Specifications

• Concrete Grade: As per IS 456-1976 (e.g., M20 or as specified).
• Reinforcement Bars: High strength deformed bars conforming to IS 1786 (Grade Fe415).
• Cover: Extra cover below ground level for columns.

Summary Diagram: Reinforcement Distribution in Rectangular Footing

Shear Reinforcement & Stirrups - IS SP:34 Key Points

1. Stirrups in Edge Beams (Clause 8.10 e)

• Stirrups must be closed loops.
• At least one longitudinal bar in each corner of the beam.
• Longitudinal bar diameter ≥ stirrup diameter & ≥ 12 mm.
• Prefer 90° hooks for ease of placing.
• Two-piece closed stirrups allowed for better placement.

2. Minimum Shear Reinforcement (Clause 8.10 f)

• Minimum stirrup area as per Fig. 8.11 (not provided here).
• Vertical stirrups spacing ≤ 0.75d (effective depth).
• Inclined stirrups (45°) spacing ≤ d.
• Maximum spacing not to exceed 450 mm.

3. Bent-up Bars (Clause 4.3.5 b)

• Bent-up tensile bars at 45° to 60° can act as shear reinforcement.
• Usually combined with vertical stirrups.
• Must be anchored per development length tables.

4. Development Length for Shear Reinforcement (Clause 4.3.5)

• For Deformed bars (fy=415 N/mm²) and Plain bars (fy=250 N/mm²), refer to Tables 4.3 and 4.2 respectively.

Use appropriate table based on bar type and concrete grade.

Summary Diagram of Shear Reinforcement Spacing

flowchart LR
    A[Effective Depth (d)] -->|Max spacing stirrups| B[Vertical Stirrups ≤ 0.75d]
    A -->|Max spacing stirrups| C[Inclined Stirrups ≤ d]
    B

Reinforcement for Beams and Haunches (IS SP Part 34)

1. Curtailment of Main Reinforcement in Beams (Clause 8.5)

• Reinforcement length relates to the bending moment diagram.
• Simplified rules apply for:
  • Continuous beams with nearly equal spans (±15% span length difference)
  • Simply supported beams
  • Cantilever beams
• Applicable mainly for beams under uniformly distributed loads.

2. Side Face Reinforcement

• Required if beam depth > 450 mm.
• Provide 0.1% of web area as reinforcement, distributed equally on two faces.
• Spacing: maximum 300 mm.
• Corner bars must be properly anchored at supports.
• Round outermost bars.

3. Shear and Torsion Reinforcement (Clause 8.14A)

• Refer to Fig. 8.32 for beam haunch reinforcement detailing.
• Vertical links (stirrups) carried through haunches with additional bars (h) parallel to haunch.

4. Main Reinforcement in Haunches (Clause 8.10.1)

• Main tensile bars continue through haunch as if haunch does not exist.
• Bars are cut off according to bending moment diagram.
• Additional bars parallel to haunch carry vertical links (see Fig. 8.33 & 8.34).

Key Specification Summary:

Simplified Curtailment Concept (Visual):

graph LR
A[Bending Moment Diagram] --> B[Determine reinforcement length]
B --> C{Beam Type}
C -->|Continuous| D[Use Fig. 8.15 rules]
C -->|Simply Supported| E[Use Fig. 8.16 rules]
C -->|Cantilever| F[Use Fig. 8.17 rules]

For

Welded Wire Fabric (WWF) & Mesh Reinforcement per IS SP Part 34 & IS 1566-1982

Key Points from IS 1566-1982:

• Types: Oblong mesh or square mesh.
• Forms: Supplied in rolls or flat sheets.
• Material: Hard-drawn steel wire.
• Properties Covered: Material specs, mechanical properties, dimensions, weight, tolerance.

Typical Specifications:

Weight Calculation Formula:

[ W = \frac{d \times L \times \rho}{1000} ] Where:

• (W) = Weight in kg/m²
• (d) = Diameter of wire (mm)
• (L) = Length of wire per m² (depends on mesh size)
• (\rho) = Density of steel = 7850 kg/m³

Mesh Schedule (Example from Table 5.9, IS SP Part 34):

Design & Detailing Tips:

• Include mesh size, wire diameter, and fitting details in structural drawings.
• Ensure proper lap length and anchorage as per IS 456 guidelines.
• Use flat sheets for slabs or rolls for curved surfaces.

flowchart LR
    A[Start: Select slab panel] --> B[Determine load & thickness]
    B --> C[Choose mesh size & wire diameter]
    C --> D[Refer IS 1566 for specs]
    D --> E[Calculate weight & spacing]
    E --> F[Include

Reinforcement Detailing for Stairs and Landings (IS SP:34 Part 34)

Key Clauses & Figures:

• Clause 10.3 & Fig. 10.3 & 10.4:

  • Show reinforcement for stairs supported at ends of landings and flights.
  • Main reinforcement spans from outer edge to outer edge (Fig. 10.3) or inner edge to inner edge (Fig. 10.4).

• Clause 10.9 (Table):

  • Specifies reinforcement for handrail supports.
  • Reinforcement must pass around pockets or inserts for handrail posts with adequate anchorage.

Important Specifications:

• Main reinforcement length should be the greater of Ld or 0.31m (Ld = development length).
• Use distribution steel and flexible material pads at supports to accommodate stresses.
• Anchoring bars must be properly bent and anchored into the main concrete body.

Typical Reinforcement Details (from Table & Figures):

General Reinforcement Rules:

• Provide main bars in tension zones (tread and riser junction).
• Distribution bars perpendicular to main bars for crack control.
• Handrail pockets require reinforcement bars bent around and anchored.

Summary Diagram (Stair Reinforcement Layout)

flowchart TB
    A[Landing] --> B[Main Reinforcement Bars]
    B --> C[Distribution Bars]
    C --> D[Handrail Pocket Reinforcement]
    D --> E[Anchorage into Main Concrete]
    style B fill:#f9f,stroke:#333,stroke-width:2px
    style C fill:#bbf,stroke:#333,stroke-width:2px
    style D fill:#fbf,stroke:#333,stroke-width:2px

Reinforcement for Retaining Walls and Tanks (IS SP:34)

1. Base Reinforcement for Circular Tanks (Clause 11.5.5.2):

• Base must be doubly reinforced to resist downward pressure (tank full) and upward soil pressure (tank empty).
• Use square mesh fabric for base reinforcement; corner bars require detailed drawings (Fig. 11.23).
• Main bars in the top layer should be placed at right angles for effective stress distribution.

2. Reinforcement Ratios (Clause 11.2):

• Horizontal reinforcement spacing: ≤ 3 × wall thickness or 450 mm, whichever is less.

3. Retaining Walls (Clause 11.9):

• Reinforcement must allow continuity, avoid abrupt laps, and maintain cover against earth faces (use leveling courses).
• Expansion joints should incorporate waterstops and allow shear transfer (Fig. 11.18).
• Additional steel may be required near counterforts due to earth compaction and shrinkage stresses.

Summary Table for Reinforcement in Retaining Walls and Tanks

flowchart

IS SP:34 (S&T) - Key Points on Flexural Members & Deep Beams

1. Flexural Members (Clause 12.1 & 8.5)

• Curtailment of Reinforcement (Clause 8.5 & 4.6):
  • Main reinforcement can be curtailed based on the bending moment diagram.
  • Simplified curtailment rules apply for:
    • Continuous beams (Fig. 8.15)
    • Simply supported beams (Fig. 8.16)
    • Cantilever beams (Fig. 8.17)
  • Conditions:
    • Uniformly distributed loads
    • Continuous beam spans differ ≤ 15%
• Side Face Reinforcement:
  • Required when beam depth > 450 mm
  • Provide 0.1% of web area distributed equally on two faces
  • Spacing: max 300 mm
  • Corner bars must be properly anchored at supports
• Shear & Torsion Reinforcement: Refer Clause 8.14A for detailing.

2. Deep Beams (Section 11)

• Deep beams are treated as special structures with distinct load transfer mechanisms (strut-and-tie models).
• IS SP:34 provides guidelines for reinforcement detailing and design principles distinct from normal beams.
• Typically, deep beams have span-to-depth ratio < 2 and require careful shear reinforcement.

Typical Curtailment Formula:

[ L_c = \frac{M_{max}}{M_x} \times L ]

• (L_c): Length of reinforcement from support
• (M_{max}): Maximum moment in span
• (M_x): Moment at section x
• (L): Span length

Summary Table: Reinforcement Curtailment (Simplified)

flowchart TD
    A[Flexural Member] --> B[Curt

IS SP Part 34 Key Points on Supports, Spacers & Cover Maintenance

1. Choice of Supports (Clause 13.1, Table 13.1)

Supports are evaluated on economic & technical factors with grades (1=excellent to 4=not recommended):

2. Factors Affecting Device in Concrete

3. Spacing, Cover & Diameter (Clause 9.2)

• Use metal spacers with plastic caps to maintain cover & spacing.

Key Specifications for Inspection and Welding Procedures (IS SP Part 34)

1. Inspection

• Refer IS 822-1970 for the Code of Procedure for Inspection of Welds.
• Inspection covers visual, dimensional, and defect evaluation of welds.

2. Welding Edge Preparation (Manual Metal Arc Welding)

• Edge preparation is crucial for weld quality; follow Table A-1 below:

• Symbolic representation defines bevel angles and root gaps for clarity.

3. Welding Procedure

• Flash butt welding should follow the Indian Standard Recommended Procedure for Flash Butt Welding (under print).
• Electrode and filler rod selection per Table A-1.1 (Clause 1.3.1.1).

Summary Diagram of Edge Preparation Types

graph LR
A[Root Accessible] -->|Back-chipping & sealing| B[60° angle, 0-3 mm gap]
C[Root Inaccessible] -->|Copper backing| D[60° angle, 0-3 mm gap]
E[General Use] --> F[60° angle, 0-1.5 mm gap]
G[Root Inaccessible] --> H[20° angle, 5-6 mm radius, 1.5-4 mm gap]

Note: Always ensure welds comply with IS 822 inspection criteria and edge preparations as per Table A-1 for optimal weld integrity.

Key Specifications & Details for Welding and Lap Joint (IS SP Part 34):

1. Lap Weld Dimensions (Clause 1.3.2.3 & Table A-2)

• Throat thickness must develop full bar strength.
• Minimum throat thickness and gap for lap welds:

• Max gap for bent bars: 6 mm.
• For gaps > 6 mm, use splice bars/plates with gap ≤ 0.25 × bar diameter or 5 mm (whichever is less).
• Splice plate area ≥ 105% of larger bar area.

2. Welding Procedure (Clause 2.2.3.3)

• Arc struck mid-joint (Fig. A-8).
• Electrode movement varies by joint position (horizontal/vertical).

3. Joint Location (Clause 1.5)

• Welded joints must be staggered along member length.
• Avoid placing joints in highly stressed zones.

Visual Summary (Lap Weld Joint)

flowchart LR
    A[Bar 1] -->|Lap Weld| B[Bar 2]
    B --> C[Throat Thickness: per Table A-2]
    B --> D[Gap ≤ 6 mm if bent bars]
    D --> E{Gap > 6 mm?}
    E -- Yes --> F[Use Splice Plate/Bar]
    E -- No --> G[Direct Lap Weld]

This ensures weld strength matches bar strength and maintains structural integrity.