2" Composite Slab - 12 ft. Span

[XR250]

I am designing a residential music studio with a suspended slab over a full basement. A 12 ft. slab spans works out nicely with the basement layout. Looks like a 6” total thickness slab on 18” ga shored composite deck will span 12 ft supporting a 145 psf superimposed live load. I am worried about vibration. Does anyone have any first-hand experience with slabs of this type spanning this far? There will likely only be a few humans occupying this space at any given time and the equipment is not super heavy.

Thanks

 

[jittles]

Pretty sure that deck manufacturers typically just give a span ratio as a guideline for vibrations.

Low to mid-20's per Verco is suggested. You're at about 24, probably just fine.

I've done 6" total thickness over W2 decking at upwards of 10' span and it performed just fine. On that note, why not a different deck that can be un-shored? W2 or W3 I imagine would work, and you shouldn't have any fire rating concerns in a residential application. Same cost for deck, less concrete, no shoring...

 

[KootK]

X2 for jittles post. I think you're ok here

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235

 

[271828]

Calculate the natural frequency of the slab, idealizing it as simply supported. It's probably very high. If so, then the slab won't contribute much to vibrations.

 

[XR250]

Thanks for the feedback. Not sure why I was stuck on 2" deck - probably because I want the drops and it works better for projects around the home :>

 

[XR250]

FWIW, this is going to be a finished slab. They will be scoring it a 4 ft. o.c. each way for appearance sake. The 2" gives me more concrete above the deck to work with.

 

[txeng91]

XR250, based on your responses I’m wasn’t sure if you were moving towards a deeper unshored deck or not. If so, I would consider hedging some on the manufacturer tables for their max construction spans. I had a recent project where I got pushed into spacing out the joists and the construction span was maxed out in a few locations. If you read through the manufacturer specs, you will see that the deflection criteria for loading during construction is pretty low (L/180 or 1” I believe). The contractors were not very comfortable with it when they poured the deck and ended up shoring longer spans on subsequent pours.

 

[XR250]

Thanks txeng91.
After discussions with the Arch. and Contractor, we revised the layout to give 10 ft. max. spans.

 

[msquared48]

Initially, according to the title, you had me going here. I thought you were using a 2” composite flat slab spanning 12 feet. That concerned me just a little. Now see that it is 4 over 2” deck. No worries.

Mike McCann, PE, SE (WA)