Design of Beams MCQ with answer and solution

Concept

Maximum tension reinforcement limit in beams

Formula

Ast = 0.04 × b × D

Step-by-step solution

1. According to IS 456, maximum limits are prescribed on reinforcement in beams to avoid congestion and ensure proper concrete placement. 2. The maximum area of tension reinforcement in a beam shall not exceed 4% of the total cross-sectional area (bD). 3. Therefore, the maximum area of tension reinforcement is 0.04 bD. Answer: A

Explanation

Standard reinforced concrete design codes specify that the area of tension steel in a beam must not exceed 4 percent of the gross cross-sectional area. This upper limit prevents congestion of steel bars, allowing concrete to flow properly around the reinforcement during casting. Thus, option A (0.04 bD) is the correct maximum reinforcement limit.

Why the other options are wrong

A) Maximum tension reinforcement in beams is limited to 0.04 bD by IS 456. B) A limit of 0.02 bD is lower than the permissible 4% maximum steel area specified for beams. C) The 0.08 bD limit represents the maximum reinforcement percentage allowed for columns, not beams. D) A steel area of 1.10 bD exceeds the total gross cross-sectional area of the beam.

Shortcut

Maximum beam reinforcement is capped at 4% of gross area (0.04 bD).

Common mistake

Confusing the maximum tension reinforcement limit for beams (4% or 0.04 bD) with that of columns (8% or 0.08 bD).