Design of Slabs MCQ with answer and solution

Concept

Minimum thickness requirement for flat slabs

Formula

NONE

Step-by-step solution

1. IS 456 specifies minimum thickness limits for flat slabs to satisfy structural integrity and deflection criteria. 2. As per IS 456 recommendations, the overall thickness of a flat slab shall not be less than 125 mm (12.5 cm). 3. Therefore, the total minimum thickness required is 12.5 cm. Answer: C

Explanation

Standard guidelines in IS 456 mandate that the minimum total thickness of a flat slab should not be less than 125 mm (12.5 cm). This minimum depth requirement ensures adequate deflection control and prevents punching shear failure around column heads without excessive shear reinforcement. Therefore, option C correctly states the minimum required thickness of 12.5 cm.

Why the other options are wrong

A) A total thickness of 8.5 cm is below the minimum code specification for flat slab construction. B) A thickness of 10 cm does not satisfy the structural and deflection control criteria mandated by IS 456. D) While 15 cm is common in practical designs, the minimum total thickness requirement specified by the code is 12.5 cm.

Shortcut

Minimum thickness for a flat slab is 12.5 cm (125 mm).

Common mistake

Confusing the minimum thickness limit of flat slabs (12.5 cm) with the lower minimum thickness limits of conventional slabs.