DESIGN

Effective Span (Beams & Slabs)

Span used for design calculation — per IS 456 Cl. 22.2 — lesser of (clear span + effective depth) and (centre-to-centre distance of supports).

Also calledeffective spanleffeffective span beameffective span slabis 456 effective span

Related on InfraLens

CODES

IS 456

Definition

Effective span Leff per IS 456 Cl. 22.2: (a) Simply supported / continuous: lesser of clear span + d, or c/c of supports; (b) Cantilever: clear projection + d/2 (or to face of support); (c) Continuous with supports wider than 1/12th of clear span and ≤ 600 mm: clear span + d, or c/c if smaller. The effective span drives moment, shear, deflection check, and depth selection.

Typical values

Simply supported beam (Cl. 22.2.a)min(clear span + d, c/c)

Cantilever (Cl. 22.2.b)clear projection + d/2

Continuous wide-support (Cl. 22.2.c)min(clear span + d, c/c)

Where used

Moment + shear calculation
Deflection limit check (span/depth ratio)
Slab thickness selection (Cl. 23.2.1)

Acceptance / threshold

Per IS 456 Cl. 22.2 — pick the lesser of the two governing dimensions for design.

Site example

Beam between 230 mm columns, clear span 5 m, effective depth 450 mm: Leff = min(5000 + 450, 5230) = 5230 mm = 5.23 m. Use this for moment computation.

Frequently asked

What is effective span of a beam?

Per IS 456 Cl. 22.2: lesser of (clear span + effective depth d) and (centre-to-centre distance of supports). Drives moment, shear, and deflection design.

Effective span of cantilever?

Per IS 456 Cl. 22.2(b): clear projection from face of support + d/2.

Related design terms

Structural Thumb Rules

Rules of thumb for slab/beam/column sizing

Reinforcement Limits (Min/Max %)

Min 0.12% slab, 0.85% beam tension; max 4% column per IS 456

Formwork / Shuttering

Stripping time: slab 7d, beam soffit 14d, column 16-24h

Scaffolding & Safety

Scaffolding safety per IS 3696

Rebar Spacing (Min/Max)