Design of Beams MCQ with answer and solution

Concept

Interaction check for axial tension with bending (working stress)

Formula

σ_at,cal / σ_at + σ_bt,cal / σ_bt ≤ 1

Step-by-step solution

1. The interaction check adds the ratio of actual to permissible stress for each action. 2. The sum must not exceed 1.0 (a safe design).

Explanation

When axial tension and bending act together, the stresses combine. The check is that the sum of the stress ratios stays within unity; a "≥ 1" condition would indicate failure.

Why the other options are wrong

A subtraction would reduce the stress ratio, which is unsafe, and a "≥ 1.0" criterion indicates overstress.

Shortcut

Interaction: sum of ratios ≤ 1.

Common mistake

Using a minus sign.