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
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 terms
Clear Span vs Effective Span
Clear distance between supports vs the span used in analysis (effective span)
Deflection Limits
Span/250 (final), span/350 (after partition). IS 456 Cl. 23.2 — use span/depth ratios for control.
Deep Beam
Beam where span/depth ratio is below 2.5 (simply supported) or 2.0 (continuous). Strut-and-tie design per IS 456 Cl. 29.
Reinforcement Limits (Min/Max %)
Min 0.12% slab, 0.85% beam tension; max 4% column per IS 456
Effective Flange Width (T-Beam)
The slab width acting with a beam web as a T/L-beam compression flange
Shear Span (a/d Ratio)
Distance from support to load over depth — distinguishes beam vs deep-beam action
Limit State Design (LSD)
Modern design philosophy ensuring two limit states: ULS (collapse) and SLS (deflection, cracking). IS 456 Cl. 35.
Formwork / Shuttering
Stripping time: slab 7d, beam soffit 14d, column 16-24h
Balanced Section
Section where concrete crushes (0.0035) and steel yields (fy) simultaneously. xu = xu,max per IS 456.
Stirrups / Shear Reinforcement
Shear reinforcement in beams/columns