Built-up Columns MCQ with answer and solution

Concept

Lacing is designed for a transverse shear of 2.5% of axial force. With two parallel lacing systems, each system takes half of it.

Formula

V_t = 0.025 P; shear per lacing system = V_t / 2 = 0.0125 P

Step-by-step solution

1. As per IS 800, total transverse shear for lacing: V_t = 2.5% of axial force P. 2. There are two parallel lacing systems (two planes). 3. Each system takes V_t / 2 = 2.5% / 2 = 1.25% of P. 4. Answer is (B).

Explanation

IS 800 asks lacing to resist a transverse shear of 2.5% of the column axial load. When there are two parallel lacing planes, this shear is shared equally. So each lacing system is designed for 1.25% of the axial force.

Why the other options are wrong

A is the total shear, not the share of each system. C and D are far too large and are not code values.

Shortcut

One lacing plane = 2.5% P; two planes = 1.25% P each.

Common mistake

Choosing 2.5% and forgetting to divide between the two parallel systems.