Design of Beams MCQ with answer and solution

Concept

Lateral Torsional Buckling

Formula

N/A

Step-by-step solution

1. Review the given question regarding the prevention of Lateral Torsional Buckling (LTB) in steel beams. 2. Recall that LTB occurs when the compression flange bends sideways and twists under load. 3. Identify that providing adequate lateral support to the compression flange prevents LTB and select Option (b) as the correct choice.

Explanation

Lateral torsional buckling happens when the top part of a beam (the compression flange) bends sideways and twists under heavy loads. Providing proper lateral support directly to this compression flange holds it firmly in place, preventing it from moving sideways or twisting.

Shortcut

To remember how to prevent Lateral Torsional Buckling (LTB), use the mnemonic "Brace the Compression": - Buckling Site: LTB occurs specifically in the Compression Flange because it is under compressive stress. - Prevention Rule: Providing Lateral Support/Bracing directly to the Compression Flange stops sideways movement and twisting.

Common mistake

A common mistake is selecting option C by incorrectly assuming that increasing the span improves stability, whereas longer unbraced spans actually increase the risk of lateral torsional buckling. Another frequent mistake is selecting option A by assuming that using a thinner web reduces overall weight and buckling, when in reality a thinner web can increase slenderness and lead to web buckling issues rather than preventing lateral torsional buckling.