Various types of roof trusses include king post truss scissor truss north light truss etc.
Purlins roof design.
Designing of roof trusses as per is 800 and is 875 part 1 2 and 3.
In structural steel or aluminum construction purlins usually w shapes or channels transfer roof loads to the major structural elements supporting the roof.
The designis based on the maximum yeild strength mn fysx as stated in the aisc manual 13th ed.
The shape of cee purlins does not allow end lapping they are butted together.
Maximum span is 11 4m.
Butted purlins can be used over supports or within the depth of the supporting section.
Welded together they can be used as columns braces and ties.
Purlins are 2 by 4 feet and are installed much like metal roofing.
Metal roof purlins are installed horizontally under metal roofs.
The type and spacing of purlins is a design consideration which depends upon the incident roof loads as well as the limiting lengths of sheeting to be used.
They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top.
They give added support to the roof and also provide a nailing surface for the end panels and drip edge.
The plane surface of c purlin on its one side has made it a preferred material for cladding due to its easy installation on concrete structures or steel.
Roof purlin are members used to directly support roof sheeting materials and could be made of timber or steel.
The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge.
A common arrangement is a rafter and purlin system which combines purlins and rafters.
Details are on page 32.
Description this spreadsheet is to be used to check the adequacy of roof purlins for a specified combination of loads.
Butted purlins are also useful for frames which have large clear spans and where large frame deflections may be harmful to continuous purlin systems.
This spread sheet can only be used for load combinations with two variables.
In timber construction purlins are nailed to the rafter or supporting trusses while in steel roof construction they are welded or bolted to the rafters or trusses by the means of cleats.
