Roof Uplift 1

[dik]

We have a small uplift load. Is anyone aware of literature that permits the deck to help with lateral stability of steel purlins? An Lu of 26 feet is a bit excessive. Can staggering the roof puddle welds provide a 'little' flexural resistance to assist with lateral support?

Dik

 

[jike]

We would either upsize beams or add a row of bottom flange bridging similar to joists. X-brace bridging at ends.

 

[paddingtongreen]

If you mean for the bottom flange, the answer is "No". I agree with jike on the bridging idea.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[dik]

Thanks... Dik

 

[WillisV]

You can use a Cb factor of 2.0 for uplift loads in a simply supported beam with a decked top flange - this can help a good bit with the moment capacity. This stems from Galambos' stability work, but will also be detailed in the Commentary to the 2010 AISC Specification.

 

[steellion]

Jike, you can also use angle kickers to brace the beam bottom flange to bring the Lb down.

Willis, can you provide a link to that paper? Being able to use a Cb of 2.0 would help.

 

[dik]

Thanks... Dik

 

[WillisV]

Dik - it is from Yura's 1995 "Bracing for Stability-State-of-the-Art" proceedings from the structures congress.

I don't have a link to it. Best I can do for now is link you to AISC's steel design after college slides:

http://www.aisc.org/WorkArea/showcontent.aspx?id=2778

(Warning this takes forever to download). It is presented on PDF page 29 (slide 49) and discussed before that.

As stated before it will also show up in the Commentary to Chapter F in 2010.

 

[dik]

Used a steel strap at mid-span with X-bridging at ends to provide added support... problem solved. The material by Willis was excellent and increased the capacity by 2x, but I needed 3x... great publication.

Dik