Industrial Roof Trusses MCQ with answer and solution

Concept

Purlins in Roof Trusses

Formula

N/A

Step-by-step solution

1. Identify the structural member in an industrial roof truss that directly supports the roof covering material. 2. Recall that purlins are horizontal structural members laid across roof trusses to directly carry the roof sheeting. 3. Compare the given options and select Option (d) as the correct choice.

Explanation

Purlins are horizontal structural beams that run across the roof trusses to directly support and hold the roof sheeting or covering material in place. They transfer the weight of the roof sheeting and external loads, like wind and rain, directly to the main frame of the roof truss.

Shortcut

To remember the role of Purlins, use the memory trick "Purlins = Panel/Paper support": - Purlins: Directly support the roof Sheets/Panels. - Principal Rafters: Support the Purlins, not the roof covering directly.

Common mistake

A common mistake is selecting Option A (Principal Rafters) by confusing them with Purlins. Students often think of principal rafters as the main members supporting the roof, but in reality, principal rafters support the purlins, whereas purlins are the horizontal members that directly support the roof covering material.