Gymnasium on Suspended Wood Floor

[KootK]

I've got a client who wants a second floor gymnasium. Indoor track, basketball court, aerobics studio... the works. But they don't want to use concrete or steel. They want wood. Obviously, this raises concerns on the vibration front.

On a gut feel level, is there any wood framing system that you would feel comfortable using to support a gymnasium? Concrete topped cross laminated timber is all that I can think of. And I'm not even too thrilled about that.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[MikeHalloran]

Find a shipbuilder with a big stock of old growth (large) oak timbers?


Mike Halloran
Pembroke Pines, FL, USA

 

[Guastavino]

Kootk,

So I went to a seminar where a guy was the lead engineer for a timber composite beam project. Was crazy expensive but unbelievable capacities. You can do some research on it but he had to have load tests etc. amazing building though

http://cenews.com/userfiles/image/SE_092013_21_1.jpg

Is a link to a picture. It's the Army corps of engineers building in Washington state or Oregon, or somewhere on the west coast. Hope that helps. But I'm with you, wood for that seems bad. Creep?

What about wood sleepers with a wood floor?

 

[dhengr]

KootK:
Are you sure he doesn’t mean a wood playing floor on cork (some resilient underlayment) or on sleepers or some such, which is then atop a real structural floor system? That wood playing floor is softer under foot for a playing surface. Alternatively, tell him he better have a use for lots of closets or other small rooms, because under his floor system there are going to be bearing walls ever 6, 8 or 10' o/c, in both directions. Maybe he just wants one great big trampoline. I don’t know of a long span wood system which won’t be problematic for those kinds of loadings. Maybe an industrial grade GlueLam system, lower stress levels, therefor larger size beams and stiffer, closely spaced; with 2x’s spanning btwn. the GlueLams and supporting a plywd. subfl. The 2x’s and plywd. could be some sort of a stressed skin, pre-built panel system, bearing on ledgers on each side of the GlueLam beams, with the top plywd. skin lapping over the top of the GlueLam, and glued-n-screwed down to it.

 

[Trenno]

Steel reinforced timber beams?

 

[Trenno]

 

[XR250]

What is the span for the main members?

 

[manstrom]

I'd be more worried about vibration in steel than in wood. Glulams or deep prefab trusses. Thick plywood and a lot of gypcrete.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[XR250]

@Trenno;

That looks pretty scary to me. Not a whole lot of cover on that steel.

 

[jayrod12]

I would expect it to be slightly spongy after a while, once the connection slip had relaxed out of it. But I do agree with manstrom that steel would be tougher to control vibration (although steel affords you the ability to put a thick slab on it).

Although I think about the old warehouses that I've see around here that are vertically oriented solid 2x6 decking/joists (2x6 @ 1.5"o/c) spanning to huge timber beams. Rock solid, and 100 years old.

You would need fairly tight spacing on the supports though.

 

[KootK]

Thanks for all the creative suggestions.

The spans are about 12m with no incidental walls below. And the intent is definitely structural wood, not just wood flooring. Although the ability to recess the wood flooring is definitely an issue.

I can select glulam beams to mimic the stiffness of steel beams. And the CLT handbooks constantly tout it as equivalent to concrete slabs. So that's what's got me thinking 50 mm concrete over 10" CLT over 27" glulam. It would be a heck of a floor plenum but should be roughly equivalent to a steel floor with a beefy concrete deck.

A part of what's got me rattled here is that I've never done any basketball courts above grade in any material. I haven't seen much of it either. A gym that I used to frequent had a rooftop tennis court over deep steel joists and that seemed to work fine. I'd be pretty confident with a court on a beefy suspended CIP slab.

So... Even if it was a steel floor, would a suspended court be unwise? As pointed out above, a steel floor may well be more vibration prone than a wood floor.



I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Archie264]

Here's a picture of a running track suspended above a gym. From the photo it looks like the frame is likely steel but the flooring is wood. Not your situation but it might provide a reference point of some sort. See Link.

 

[manstrom]

36' is not a great span, but not terrible. Talk to the owner to manage expectations.

I would be curious to see how CLT compared in cost to steel / concrete. Regardless, it wouldn't be the main structure. I don't think you could span 36' on CLT, you'd still need some glulams.

Run a few scenarios. Maybe glulams at 4' or so with 2xs running between them. Plywood with a LW concrete topping (3") or so. That should be a decent floor.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

 

[XR250]

Why bother with concrete topping? Seems like all wood construction would give a nice resilient system.
I am thinking deep glulams about 10 ft. O.C. with a conventional 2x10 floor system.

 

[Signious]

There is a great intro video on post tensioned wood & cable systems at Candadian Wood Councils webinar section. Depending on the architectural goals of the project it could be a solution.

 

[bookowski]

Not sure about the wood but if the numbers work for concrete over CLT I think it'd be ok, as you said may be better than steel.

I have done one that was 2nd floor double full size basketball court over a school library, 4th floor another double bball court over the 1st one, and at roof the same sized area for rooftop playfield. It was steel with slab on deck. I think we did a somewhat thicker than usual slab and normal weight. The 1st level court which was over a library was supported by columns in the library at a somewhat typical grid. For that one we had a concrete floating slab over the structural slab. The overall interaction of the floating slab + base slab was not clear and the floating slab guys said to just check the base slab frequencies but I'm sure it is quite helpful. We also added rebar to the slab on deck to create moment continuity for the steel beams per the aisc design guide (beams were designed without considering this but it was considered in the stiffness). Upper floors were large trusses supporting steel framing with same slab on deck. We tried to add mass and irregular framing where possible, but nothing too tricky. We never got the numbers by analysis to fully get there but the client ok'd where we were at as the cost really gets non-linear chasing the stiffness at some point. The acoustics consultant did floor frequency testing after it was complete and it was much better than our numbers and there have never been any complaints that I know of. Not much help on the wood front - but in general I think above grade is ok if your numbers work.

 

[TehMightyEngineer]

Not sure how much it helps but the university were I got my BS finished this monstrous waste of money the year before I graduated:

UMaine does a lot of research with engineering composites, mostly glulam timbers and glulams with fiber reinforced tension faces. I imagine to show this off they had the architect of the "New Balance Student Recreation Center" (eye-roll) use a lot of wood glulam beams.

Anyway, it has a very large span over the pools done in all wood and the basketball courts have a suspended running track. As the framing for the track is hidden it could be steel or wood. Overall it uses a lot of engineered lumber and, having used it, would rate it as probably the least vibrating gym I've been in.

Also, if you want, try getting in contact with Dr. Habib Dagher, P.E.

http://composites.umaine.edu/contact-us/faculty-and-staff/dr-habib-dagher-p-e/

He's probably close to the forefront of composite wood beam design and could at least point you in a good direction.

Maine Professional and Structural Engineer.

http://www.fepc.us

 

[xp1]

UT Austin, University of Houston, and Rice University in TX all have above grade basketball/running tracks, I think it may be popular for higher education facilities and you might look into them as a reference.

 

[KootK]

Thanks for all of the excellent advice everyone. In answer to some specific comments:

Regardless, it wouldn't be the main structure. I don't think you could span 36' on CLT, you'd still need some glulams.

It's shaping up to be glulam at a 10' module so yes, CLT + glulam it seems.

Why bother with concrete topping?

Yeah, it looks odd to have a system that is wood CLT + concrete + topping + wood flooring. Somehow, throwing some concrete on there just feels good for vibration purposes. Once I figure out how to run the numbers, I'll try it both ways.

There is a great intro video on post tensioned wood & cable systems at Candadian Wood Councils webinar section.

I want to see this. Any chance you can share a link? I googled... I swear it.

Not much help on the wood front - but in general I think above grade is ok if your numbers work.

Your example in steel and those provided by others are enormously helpful. Just knowing that a non-concrete above grade court is viable is a big relieve. And, as we've discussed, I'm confident that a comparable CLT system can be developed.

@njlutzwe/TME: thanks for the composite recommendations. I'm considering this as a locally available option: Link

For those who may be curious, some schematic work is shown below. It's still early days but I'm happy to accept any advice offered

.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TehMightyEngineer]

"Sexy steel rods and post". Ahahahahahah, I love it. Please tell me this went to the client.

Yeah, that timber-concrete composite floor system looks great. Still seems like steel would be cheaper but this will definitely be a good looking gym if they can stomach the cost.

Maine Professional and Structural Engineer.

http://www.fepc.us