IS 456:2000 CLAUSE 26.2.1 & 26.2.5

Development Length (Ld) & Lap Splice Checker

Calculate mandatory anchorage length, lap splice distances for tension & compression bars, standard hook equivalent allowances, and bond stress multiplier checks.

1. Rebar & Concrete Specifications

Bar Diameter ϕ (mm)

Bar Type (Bond Surface)

Concrete Grade (fck)

Steel Grade (fy)

2. Structural Stress & Splice Condition

Type of Member Stress

Splice Staggering

End Anchorage Hook

Development Length (Ld)

-- ϕ

-- mm

Formula: L_d = (φ × 0.87 f_y) / (4 τ_bd)

Design Bond Stress (τbd):-- MPa

Minimum Lap Length (Cl. 26.2.5):-- mm

Hook Anchorage Credit:-- mm

Net Straight Anchorage Needed:-- mm

Anchorage & Lap Splice Schematic

IS 456 Cl. 26.2

IS 456:2000 Development & Splice Length Rules

1. Basic Formula (Cl. 26.2.1)

The calculated development length ($L_d$) provides necessary grip between concrete and steel:

Ld = (phi * 0.87 * fy) / (4 * tau_bd)

For HYSD/TMT bars, τ_bd is boosted by 60%. For compression bars, τ_bd is boosted by an additional 25%.

2. Lap Splice Limits (Cl. 26.2.5.1)

• Tension Laps: Greater of L_d or 30φ.

• Compression Laps: Greater of L_d,comp or 24φ.

• Maximum Bar Size: Lap splices are strictly not permitted for bars larger than 36 mm; mechanical couplers or welding must be used.

3. Hook Anchorage Value

Per Clause 26.2.2.1, standard bends contribute toward development length:

• 45° bend: $4\phi$ equivalent.

• 90° standard bend: $8\phi$ equivalent.

• 180° standard hook: $16\phi$ equivalent.