Design of Slabs MCQ with answer and solution

Concept

Minimum thickness of a flat slab

Formula

NONE

Step-by-step solution

1. Flat slabs are reinforced concrete slabs directly supported on columns without intermediate beams. 2. According to IS 456-2000 clause 31.2.1, the thickness of a flat slab shall not be less than 125 mm. 3. This minimum thickness ensures adequate shear strength and deflection control. Answer: A

Explanation

IS 456-2000 explicitly specifies that the minimum thickness of a flat slab shall not be less than 125 mm. This minimum depth requirement ensures adequate structural resistance against shear forces, punching shear, and serviceability deflection limits. Thinner slabs are prone to excessive deflection and sudden punching shear failure around columns.

Shortcut

Minimum thickness of a flat slab = 125 mm.

Common mistake

Confusing the flat slab minimum thickness (125 mm) with footing or conventional slab minimums.