One-Way Slab

A one-way slab bends predominantly in a single direction. It occurs when the slab is supported on two opposite edges only, or when it is supported on all four edges but the longer span Ly exceeds twice the shorter span Lx (Ly/Lx > 2) — in that case nearly all the load travels along the short span to the long supports.

Main (flexural) reinforcement runs parallel to the short span; distribution steel (minimum 0.12% of gross area for Fe 500, 0.15% for Fe 415, per IS 456 Cl. 26.5.2.1) runs perpendicular to resist shrinkage, temperature and any minor secondary bending. Design is per metre strip as a beam: Mu = wuLx²/8 (simply supported) or via Cl. 22.5 moment coefficients for continuous slabs. Thickness is usually governed by the span/effective-depth deflection limit of IS 456 Cl. 23.2 (e.g. 20 for simply supported, 26 for continuous, before modification factors).