Correct Answer - Option 1 : 4.5 to 6 m
Explanation:
For economical spacing of truss,
The cost of truss should be equal to twice the cost of purlins plus the cost of roof covering.
t= 2p + r
where t= cost of truss, p= cost of purlin, r= cost of the roof.
However, the above expression is used to check the spacing of the roof truss.
It can not be used to design the spacing as spacing does not occur in the equation. As a guide, the spacing of roof truss can be kept 1/4 of the span up to 15m and 1/5 of span for 15-30 m span of roof trusses.
Given,
Spacing of Truss = 15 m to 30 m
So spacing should be
Maximum limit of spacing = 1/5 of 30 m = 6 m
So the correct option is Option 1 as spacing of truss is between 4.5 m to 6 m
