Cold Formed Purlin Cleats/Clips

[slickdeals]

I don't have much experience with cold-formed structures. I was looking at some details from PEB suppliers that shows a clip/cleat welded to a roof beam. The Z purlin is bolted to this clip.

Is rotational restraint at the support provided by the weak axis bending capacity of the clip? How do you calculate what thickness is needed? If you can point me to any literature, that would be great.

It’s no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don’t know which half - LORD KELVIN

 

[hokie66]

That depends on the height of the cleat (the distance from the top of the purlin to the top of the rafter). You need to assess the force in the plane of the roofing, and distribute that between the cleats. Sometimes, with tall cleats, angles are needed to resist the bending due to the planar force.

See Page 9 of the following for sizes of cleats we use in Australia, assuming the purlin is just above the rafter.

 

[hokie66]

Don't know how that happened. Will try again.

 

[slickdeals]

Hokie, thanks. Could you please re-post your link? It appears to be broken.

Any literature on assessing the forces on the roof? Are we talking about the horizontal component of gravity loads? Won't some of these forces be carried by the anti-sag /roll rods or bridging?

It’s no trick to get the answers when you have all the data. The trick is to get the answers when you only have half the data and half that is wrong and you don’t know which half - LORD KELVIN

 

[hokie66]

I think the link should work now. Yes, the gravity load as resolved parallel to the roofing. And yes, the bridging will carry its share over the ridge or into a stiff element at top or bottom of a skillion roof.