Rick check out the load tables in IBC (or any other building code):  garages for passenger cars - even commercial parking garages - have prescribed loads that are only about half of what's required for a basketball court/gymnasium.

There are plenty of examples of regulation NCAA venues that have other uses above them - I can think of several universities that have stacked gymnasium spaces, one above another - and that needs beefier structure than parking does.

Yes, there are large spans involved.  But they're not so exceptionally large that they're amazing feats of engineering, or that they require ridiculously oversized structure and super-thick walls.  This is an ordinary building type, not particularly rare.  My kid goes to preschool in a YMCA that has an Olympic-sized pool in the sub-basement, full-size gym above that at ground level, parking at the 2nd-floor level, and residential floors above that.  It's an unremarkable building - no 10 foot thick pilasters.

prescriptive loads are based on use, not construction type.  Parking for passenger vehicles is 50 lb/sf, regardless of whether it's parking on slab on grade or parking on a roof deck.  Live load for a basketball court is 100 lb/sf, regardless of construction type or what level it's on. All you need to do to verify this is look it up.   All this nonsense about jumping cars, glu-lams, and pilasters is you once again desperately trying to save face after realizing that you've exposed your lack of real experience again, and making it worse the harder you try.

"Remember, commercial parking garages for example are not under any form of prescriptive code."  Richard open IBC and look for the table that includes live loads for commercial garages.  This is beginning to remind me of when you stated in another thread that UL doesn't publish books of rated assemblies!  The big orange books could be piled all around you and you'd still deny their existence.
This "what are the live loads for a parking garage" scenario is a typical exercise in first-year structures courses, and students often start with the same misunderstandings you're displaying here. As an architect, engineer, and former statics instructor, my advice is that you would benefit from taking a real structures course taught by a practicing architect or engineer.  Your auto-didactic approach is a colossal failure here because you don't have the very fundamental understandings to see why you're wrong. 

*shrug* I haven't looked this up, but have been told on multiple occasions that in Atlanta we have to design for 100 PSF live loads on our parking decks.  I assume two things, that our structural engineer knows what he's talking about, and that when he says "for Atlanta" it's a local requirement.

Of course if I get a project with a parking deck in its scope, I'll do a bit more than assuming, but for now, that's good enough for me.

Some of the comments on this thread are hilarious. I've never designed a basketball court, but recently detailed a 2-car garage over living space. We used precast floor panels from these guys: http://www.jpcarrara.com/Produ... It would have been even easier if it wasn't a completely panelized Passivhaus. Floor panels like that wouldn't clear span a ball court, but you could have a competent structural engineer design cast-in-place reinforced T-beams like you see in most parking garages, or design steel beams to clear-span the space, with precast or cast-in-place floor panels spanning from beam to beam. The beams could even be wood: http://nordic.ca/en/projects/s.... 

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