Question

Two beams A and B are simply supported and subjected to identical loads. The two beams have same width but beam A has double the depth of beam B. The ratio of section modulus of beam A & B is –
1. 2
2. 3
3. 4
4. 8

Answer 1

Correct Answer - Option 3 : 4

\(Section\;modulus\left( z \right)\; = \;\frac{{Moment\;of\;inertia}}{{Distance\;of\;extrume\;fibre\;from\;NA}}\)

Section modulus of rectangular section = bd²/6

Where, b = width and d = depth

\(\therefore \frac{{{Z_A}}}{{{Z_B}}}\; = \;\frac{{\frac{{b \times {{\left( {2d} \right)}^2}}}{6}}}{{\frac{{b \times {d^2}}}{6}}}\; = \;4\)