1-Center Beam Floor Support. (tile deflection) 5

[EngStuff]

This is one of those projects that I need major opinions on.

I have a Mezz. that will be considered a "stage floor" that will only be supported by 1 Beam. This beam will be an HSS member which will be supported by girders that are also HSS and HSS columns. the cantilever beams might be tapered plates or tapered W-shape beams with steel cladding or combination of both. Moment connections are everywhere including a fixed base. The floor is tile. see image below.

When it comes to deflection. Since we have both cantilever beams deflecting at their ends. At the center beam, I am worried about a tension strain on the thin set and tile(cracking). I think I will end up calling for a uncoupling membrane but that might not be enough. I am also worried about a "bump" at the center beam due to deflection on both sides.

I analyzed with full dead and live load. I also analyzed with full dead with skip live loading one each side.

My question is, what do you guys think I should hold the deflection to in this case? Also, is there anything I should take into account when designing this that I might not have thought of. Any pointers? I have admittedly not dealt with a floor like this.

Floor dead load will consist of
1. Steel beams
2. 1.5B metal deck
3. 3/4 ply
4. Thin set
5. 3/8" tile
6. Misc.
(uncoupling membrane?)

 

[EngStuff]

keeping the centre beam is just inviting problems with deflection and vibration... my earlier comment about vinyl tile is still correct.

Tomorrow I will be trying to get a hold of them to push for the Vinyl or composite tile. I honestly don't think they will go for Vinyl, but I have a chance with composite.

I hate to say this, but I want to look at it as much as possible before I give up on it and forcing them to go a different route. Tomorrow I'll be also discussing vibration with them and be upfront that we probably cannot get rid of vibration. If the client is comfortable with the vibration being an issue as long as they know it's safe and get's the job done. Then the project will probably move forward.

 

[MIStructE_IRE]

Who wants real tiles on a stage anyway?! It would be too slippery....particularly with the decline after this thing deflects do much... Joking!

I’m still not convinced about lateral stability in the long direction. Can you cantilever the columns instead?

I also remain unconvinced as to the whole stiffness of this thing supported off a central beam. Stages will be subject to rhythmic vibrations dependent on the type of music played etc etc etc... You really want this thing to be as stiff as possible and you won’t achieve that with a central beam. Tell the architect you need two beams joining the frames together and that’s it! You still taper the cantilever pieces as needed and it will look fine!

 

[Enable]

I can perhaps look into making them create a "joint" in the thin set every so often. This will cause the tension strain release. they might see cracks through the grouted joints, but as long as the tile is good.

If this works out and tiles are to be had I would haul the uncoupling membrane manufacturer to site and ask what to do. See note 7 above (lol).

But your concern is valid. Most applications are concerned with center span deflection and hence, the tile surface in compression. But a tension scenario is equally a concern for grout separating (I say separating because I’d imagine it would separate from tile edge rather than crack…but haven’t put too much thought into that).

I like your idea of segmenting the tile field into smaller areas to reduce strain on any one section. Even if it pulls away it’ll be far less over a smaller field. You can use typical expansion joints to accomplish this (the very expensive uncoupling guys are super nice and also sell us the even more expensive expansion joints. See here: Super Expensive Profiles)

One of the long time members used to use the tagline, "If you're not living on the edge, you are taking up too much room." Pretty much sums up my life.

I can appreciate the sentiment. I exclusively work in the restoration and repair industry, and of that niche, I only take on hard projects that other cant or dont want to put the time into figuring out. I get bored otherwise. And it's more lucrative.

In this case though, advice by the other members above seems solid and it's a project so beyond my regular wheelhouse that better to leave it to the pros.