Practical strengthening to existing cold rolled roof purlins 1

[liam1369]

Hi All,

I am investigating a solution to strengthen some existing roof purlins for an existing portal frame roof.

There is an adjacent building being built right next to this one, so additional snow will be created due to it effectively being a parapet right next to it.

The existing purlins are metsec 'Z' purlins and are double span sleeved.

Is anyone familiar with practical methods of strengthening them? - I have heard of fixing new ones back to back but I am not sure how that could be possible with 'Z' rail purlins?

If anyone has any suggestions or has seen something done previously this will really help.

Kind regards,

Lee

 

[phamENG]

C purlins on one side fastened with self drilling screws.

 

[Tomfh]

Screw something to the side. An angle. A Plate. A channel. A C purlin. Etc. Whatever you need.

 

[bones206]

I’ve found screwing light gauge angles to be more field-friendly than channels. That said, I like to put a channel centered on the support beam to help with bearing and negative moment, then angles along the span.

Adding blocking/bridging is an effective option as well.

Lastly you can add more purlins, but it can be challenging to install.

 

[driftLimiter]

How about adding new members between the existing? Channels or Z.

 

[MRob909]

As others have said, probably the easiest option is tek screwing a light gauge angle to one side of the existing purlin. If the snow drift condition is your only concern then it should be straightforward enough.

In the past I have also introduced additional purlins to reduce the roof sheet span. These need to be smaller in depth than the existing to install, then you need them on angle cleats to ensure they sit flush to the underside of the sheeting.

 

[liam1369]

Thanks all, they can't do additional purlins between as the grid system between the top and bottom sheet does not positively connect to the new purlins.

Will tek screws be sufficient? I think bolting may be more suitable.

 

[canwesteng]

Not sure I follow why you can't add new purlins. I've always done that, for ease of calculation (you can really get into the weeds with cold formed steel) and ease of install. IT also fixes any problems you have with overloading the roof deck as well.

 

[cec17]

I have screwed and bolted light gage angles to the top and bottom so it creates an "I" shape. Using TEK screws was easier. We pre-drilled staggered holes in the angles, be mindful of splices (both purlin and angle splices, if required) and keeping continuity within the required reinforcing length.