Question

Theoretically, purlins are generally placed at

(a) only at panel points

(b) only at edges

(c) only at mid span

(d) only at corners of roof

This question was addressed to me by my school teacher while I was bunking the class.

My doubt stems from Purlins topic in chapter Design of Beams of Design of Steel Structures

Answer 1

Right option is (a) only at panel points

The best I can explain: Theoretically, it is desirable to place purlins only at panel points. They are placed at panel points to avoid bending in the top chords of roof trusses. For large trusses, it is more economical to space purlins at closer intervals.