Roof Purlin Design Example

Design of roof purlins.

Roof purlin design example.

In traditional timber truss construction purlins rest on the principal rafters of the truss. 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. Forces in roof systems as presented in chapter 5 of the new aisi. For example a roof purlin with no transversal element other than sheathing between the extremities on the compressed flange will have an unsupported length equal to its overall length.

This spreadsheet is to be used to check the adequacy of roof purlins for a specified combination of loads. C purlin cee or c purlins are shaped like a squared off letter c. For example an 8 x 4 under purlin would support the center of a row of 6 x 2 rafters that in turn would support 3 x 2 roof purlins to which the roof cladding was fixed. Roof purlin are members used to directly support roof sheeting materials and could be made of timber or steel.

This spread sheet can only be used for load combinations with two variables. They are often used for structural support in walls and as floor joists in addition to roofs. Z purlin the zee or z purlin is shaped like a letter z. First the development of forces requiring anchorage in purlin roof systems is discussed.

The four steps in the general methodology of the component stiffness method are presented. Its shape allows the purlin to overlap with others at the joints. Design of purlin solved problem by prof l agarwal. Design guide for cold formed steel purlin roof framing systems.

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.