Built-up Columns MCQ with answer and solution

Concept

Design requirements for laced built-up columns

Formula

V_t = 0.025 × P

Step-by-step solution

1. As per IS 800:2007 Clause 7.6, built-up laced columns are subjected to axial compression and shear deformation. 2. The entire column assembly must be designed for overall member buckling under the design compressive load. 3. The lacing bars and their end connections must be designed to resist transverse shear force Vt equal to 2.5% of total axial load. 4. Hence, design must account for overall buckling and shear in the lacing system. Answer: C

Explanation

Built-up compression members connected by lacing bars must be designed for overall column buckling (incorporating a 5% increase in effective slenderness to account for shear deformation) and the lacing system must resist a transverse shear of 2.5% of the axial column load.

Why the other options are wrong

A) Direct axial load alone ignores column buckling and transverse shear forces. B) Individual component buckling check is insufficient without overall frame buckling design. D) Flange local buckling is only one section classification check.

Shortcut

Laced column = Overall buckling (5% λ increase) + 2.5% P transverse shear in lacing.

Common mistake

Designing solely for axial compression while neglecting the transverse shear force on the lacing system.