Built-up Columns MCQ with answer and solution

Concept

Built-up Columns (Lacing and Battening)

Formula

V = 0.025 P (Transverse Shear Force V = 2.5% of Axial Load P)

Step-by-step solution

1. Review the given statements regarding built-up columns. 2. Recall that lacings/battens unify column components (Statement 1 is correct) and lacing system design requires resisting a transverse shear force of 2.5% of the axial load, V = 0.025 P (Statement 2 is correct). 3. Note that laced columns handle heavy eccentric loads better than battened columns (Statement 3 is incorrect). 4. Select Option (a) "1 and 2 only" as the correct answer.

Explanation

Statements 1 and 2 are correct because lacings and battens connect individual steel sections to make them function as a single solid column, and lacing bars are designed for a standard transverse shear force of 2.5% of the column's total axial load. Statement 3 is incorrect because battened columns are not suitable for heavy eccentric loads or bending moments, whereas laced columns provide better triangulation and performance under such conditions. Therefore, option A ("1 and 2 only") is the correct answer.

Shortcut

To remember key rules for Built-up Columns, use the memory rule "2.5% Shear & Laced for Heavy": - 2.5% Shear: Lacing bars are always designed to resist a transverse shear force of 2.5% of the total axial load. - Laced > Battened: Laced columns handle heavy eccentric loads/moments due to diagonal triangulation, whereas battened columns are best only for purely axial loads.

Common mistake

A common mistake is selecting Option D (1, 2 and 3) by incorrectly assuming that battened columns are more efficient for heavy eccentric loads. In reality, battened columns should only be used for axially loaded columns without significant eccentricities or moments, while laced columns are much better suited for heavy eccentric loads due to their diagonal triangulation.