Design of Beams MCQ with answer and solution

Concept

As per IS 456, deep webs need side face steel to control shrinkage and temperature cracks.

Formula

Side face steel = 0.1% of web area (half on each face), when D_web > 750 mm

Step-by-step solution

1. IS 456 says side face reinforcement is needed when web depth is more than 750 mm. 2. Total side face steel = 0.1% of web area, divided equally on both faces. 3. Spacing of these bars should not be more than 300 mm or the web thickness, whichever is less. 4. So the answer is 750 mm.

Explanation

In deep beams, the side faces can crack due to shrinkage and temperature change. IS 456 asks for side face steel when the web depth is more than 750 mm. This steel is 0.1% of the web area, placed equally on both faces.

Why the other options are wrong

A (250 mm), B (300 mm) and D (150 mm) are not the IS 456 limit. 300 mm is the maximum spacing of side face bars, not the depth limit.

Shortcut

Remember: depth > 750 mm, steel 0.1%, spacing ≤ 300 mm.

Common mistake

Students mix up the 300 mm spacing limit with the 750 mm depth limit.