Preventing lateral torsional buckling by particle board

[Navid.Nik]

Hi all,

I am calculating a mezzanine with cold-formed sections. The floor is a particle board with 38 mm thickness, and it is connected to the beams. I think the particle board can prevent the top flange of the secondary beam to buckle, but I cannot find any supporting clause in any standard code. What is your opinion on this? Do you know any supporting facts based on standards? I am designing based on Eurocode, but every other code are also fine for this

 

[kostast88]

I would imagine there would be some partial restraint. At 38mm thk it could even be a solid diaphragm.
But I doubt the particle board would not be a full restraint though - depends on the fixings. Is that through bolts on beams flange? If so then maybe.
Regardless of code your question would adjust the buckling length, and for partial restraint you should have a slightly more conservative scenario than full restraint - without much trouble. Id' go with this scenario.

PS. Cold formed sections have a bit different section calculus than hot rolled steel - so use relevant code + software.

 

[Navid.Nik]

Thank you for your response. Yes, it is connected to the flanges of the beams by bolts, so that is why I also think it can provide enough support against the torsion of the flange. Then I can calculate the buckling of the bottom flange (which is probably in tension, and I guess the reduction factor will be equal to one . Of course I am considering all the cold-formed codes and software

 

[WARose]

AISC's code provides required bracing stiffness and strength for LTB. (In Appendix 6 in the 13th edition.) That's for structural steel but I would think it would let you know if you are in the ballpark.

[red]EDIT[/red]: By the way, I'd be a little apprehensive about using particle board for anything in terms of structural support. That stuff gets wet....and it's history.

 

[KootK]

What is your opinion on this?

I'm fine with the particle board serving the bracing function and feel that's a common and natural thing to do in situations like this. Using the particle board in this way is a bit disconcerting because of it's relative impermanence compared to other materials. That said, if the particle board disappears, so does the floor load on the beams.

 

[ATSE]

Interesting note: When Prof Winters did some of the early steel bracing and buckling research, I'm pretty sure he used cardboard for bracing.
Having said that, while particle board is an economic necessity for many industries, but I would not touch it nor rely upon it for structural applications. My structures can't crumple simply because they got wet - I design 100-year structures.

 

[SWComposites]

Particle board is not a structural material.

 

[WARose]

Particle board is not a structural material.

Actually the IBC (at least the last time I looked) recognizes particle board for certain applications. (ANSI had/has a spec for it as well.)

Everybody is just scared to death of it because of the moisture situation.

 

[dik]

I would think that particle board of that thickness would be a really great lateral restraint...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Navid.Nik]

Thank you all for the information and feedback. I think the moisture is not really an issue at least for this structure since it is a mezzanine inside a factory and it is served as a storage space (not chemical nor wet materials packages etc...).

 

[phamENG]

It's also important to understand exactly what is meant by "particle board." I've heard a lot of people call 23/32" performance rated OSB floor sheathing "particle board."

There are quite a few houses with no lateral restraint but a few feet of actual particle board (ANSI A208.1) on the corners. In fact, it remains an allowable braced wall system in the 2015 IRC (PBS under Intermittent Bracing Method).

 

[Navid.Nik]

Yes, you have a good point. The particleboard in this project is 38 mm thick and its bending strength is 15 N/mm2, which seems quite strong