Design of Beams MCQ with answer and solution

Concept

Permissible deflection of simply supported beams

Formula

NONE

Step-by-step solution

1. Deflection limits for structural elements in non-industrial buildings are specified by IS 800. 2. For a simply supported beam supporting elements susceptible to cracking, the maximum permissible vertical deflection is limited to Span/360. 3. This stringent limit prevents damage to attached brittle finishes or masonry elements. Answer: A

Explanation

Deflection limits are imposed on beams to prevent serviceability failures such as cracking of finishes or partition walls. According to steel design codes, when a simply supported beam supports elements that are susceptible to cracking, the allowable vertical deflection is restricted to Span/360. This strict limit prevents excessive sagging and structural damage to brittle materials.

Why the other options are wrong

B) Span/350 is the deflection limit after erection of partitions including long-term effects. C) Span/325 applies to gantry girders supporting manually operated cranes. D) Span/300 is the deflection limit when elements are not susceptible to cracking.

Shortcut

Elements susceptible to cracking have a vertical deflection limit of Span/360.

Common mistake

Confusing the limiting deflection for elements susceptible to cracking (Span/360) with general non-industrial beam limits.