Question

Which of the following is true for economic spacing?

(a) cost of trusses should be equal to twice the cost of purlins

(b) cost of trusses should be equal to twice the cost of purlins minus cost of roof coverings

(c) cost of trusses should be equal to the cost of purlins plus cost of roof coverings

(d) cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings

I had been asked this question by my school principal while I was bunking the class.

Question is taken from Gantry Girders & Design of Industrial Buildings topic in section Gantry Girders, Design of Plate Girders & Industrial Buildings of Design of Steel Structures

Answer 1

Right option is (d) cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings

The best explanation: For economic spacing of roof trusses, the cost of trusses should be equal to twice the cost of purlins plus cost of roof coverings. This equation is used for checking the spacing of trusses and not for design of trusses.