Pool suspended on piers

[bhiggins]

I've been tasked with designing an above ground pool supported by a grid of piers (no seismic). I've got a design down but I'm wondering if there are any other special considerations I need to make. I've read to go with 0.006 Ag steel reinforcement for crack control, which controls the entire design. I doubt they can do this in one pour, is a keyway detail with a waterstop appropriate for the construction joints, similar to a retaining wall? Anything else I'm missing? See attached section detail.

 

[bhiggins]

Plan view.

 

[KootK]

I don't love the concrete opening joint rebar detailing. More than you ever wanted to know here: Link. Does the adjacent floor system provide lateral restraint to the top of the walls?



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[calvinandhobbes10]

I would want more than just a water stop keeping the pool water out of the righthand side basement/space. With 3 inches clear you will likely see a crack open up. Could you consider a diagonal bar to keep it closed?

 

[bowlingdanish]

If it is truly a water retaining structure you should design it as such. The code I am familiar with requires you to proportion steel reinforcement such that the stresses in the bars do not exceed an allowable limit, which keeps the cracks fine. Water retaining structures make me nervous though, especially with a construction joint. Can you not get a proprietary shell or coating for the pool, such that the concrete isn't the primary water retention system? I'd also specify a waterproof crystalline admixture to the concrete such as xypex, just to be sure.

 

[kipfoot]

I'd say that yes, the builder will absolutely want to use a horizontal construction joint at the base of wall. I'd suggest a key with a waterstop on the water-side of the reinforcing (example: hydrotite). This is easier to do with a single layer of reinforcing. Like BowlingDanish, I second the suggestion of an integral waterproofing (example: Hycrete w100)

Not related to your question...but:
I'm not crazy about the water level at the right hand of the section and how splashing water over the edge of the pool can seep down into your joist bearing. At minimum, I'd get rid of that edge angle there with the exposed tip.

Maybe part of the answer to this is to drop the tapered top of wall a couple inches so that the overflow goes mostly down the 8" wall and into the adjacent runnel.

 

[JAE]

The vertical reinforcement in the small wall on the far left is on the wrong side of the wall. The bar coming from the pier ONLY occurs at the pier so it can't be the primary wall stem reinforcement.



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[bhiggins]

Thank you all for your comments. According to the builder there will be a pool membrane. I've revised the detail accordingly (attached). I will specify Hycrete W1000 admixture as an added protection, (who knows if the membrane will be removed in the future).

 

[WARose]

You may want to think about sloshing (since you asked about special considerations). I did a pool (on the roof) as part of a hotel once.....and IIRC, sloshing wound up being an issue during a seismic event. (That pool was pretty big though.)

 

[bhiggins]

The piers are quite numerous and beefy, 21"-24" inch diameter, 4' embedment into undisturbed limestone, so I don't think lateral should be much of a concern. Are you implying I should apply a "sloshing" lateral load (similar to seismic, a percentage of the water weight, correct?) in addition to my design wind loads? A 1'x1'x13.5' (pool width) slice of pool water weighs 100 psf, 5%-10% would be 5 psf to 10 psf equivalent lateral "sloshing" loads. What would a responsible percentage be?

 

[WARose]

If you want to read up on it see: '350.3-06 Seismic Design of Liquid-Containing Concrete Structures and Commentary'.

 

[JAE]

I think the original post suggested that seismic wasn't a large issue - perhaps category A. Sloshing in that case would not really be a concern.

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