Swimming pool design

[lbengineer1]

Dears,

i am designing a 40x25m swimming pool on ground.

1. Do i have to create any kind of joint in it (40m) ?
2. Do i have to apply thermal gradient effect
3. What are the approximate dimensions of the raft and walls from your experience for such pool knowing that water height is 80cm

Thanks alot

 

[CELinOttawa]

1. This depends on your design and the environment in which it will give service.
2. Yes.
3. Not applicable - We would need a great deal more information to be able to help you with this level of detail.

Have you done any pools in the past? They are not as trivial as they seem!

 

[lbengineer1]

Dear CELinOttawa,

i have made cyclors and treatment stations tanks design, in which i considered thermal gradient effect with no joint at all. however, i was wondering if i have to make the same for a ground pool.

i am planning to model it on SAP, as a raft and wall with all the possible combinations of load and check the typical checks such as soil capacity, settlement, bending and shear.
is there any other considerations?
and what is the minimum dimension of pool to neglect the joint ?

 

[lbengineer1]

of course, the steel will be design for crack width less than
2mm (BS code)

 

[CELinOttawa]

Many pools are built without an engineer's involvement and give good service... I would never recommend doing so, but unless you are dealing with expansive soils, they are pretty straightforward. Olympic and other large size pools such as this require additional reinforcement to avoid joints, and in my opinion, joints should be avoided if possible.

You still haven't told us about the service environment...

 

[lbengineer1]

Dear CELinOttawa,

the site is in a mid-area between sea and mountain (average Mediterranean weather) but as you said, the soil is clayey expansive one for which we will do some treatment (strong compaction and base course fill underneath rafts).

Any advice?

 

[BUGGAR]

I have used pour strips in reservoirs to decrease shrinkage effects and eliminate joints.

 

[lbengineer1]

dear BUGGAR,

can you please explain that more?

 

[JoshPlumSE]

Obviously, you need to design for the empty case where the walls are loaded by active pressure similar to a retaining wall. This will usually control reinforcement.

 

[lbengineer1]

in fact i do not have any problem with load cases and combinations.
My only issue is the length of the pool (40m)and if i need to make a joint or thermal consideration

 

[hokie66]

You don't need a joint if you have a lot of horizontal reinforcement, in the vicinity of 0.6 x Ag. But a 2 mm crack is wide...you don't want that, and I don't think a BS code would say so.

 

[BUGGAR]

Pour strips: Breaking a concrete pour into sections, separated by strips which are cast later, after the main pours cure and shrink.

 

[lbengineer1]

Dear hokie66 ,

its of course 0.2mm not 2mm (sorry for the spelling!)

 

[ukbridge]

Not sure how big/long the pours are, but could be that you'll need some proper reinforcement to minimise early thermal cracking or it'll crack to f*** during curing. Have a look at CIRIA C660 which gives (UK-centered) guidance to calculate whether additional reinforcement is required. I'm assuming there's a similar sort of document in your country but you can probably take some guidance from there.

BUGGAR's method is a clever one. You need to be careful that the intermediate units are not too large though as pouring intermediate units provide a lot more thermal restraint than just doing sections piecemeal. Contractors in the UK love this method for obvious reasons, but for heavy duty stuff is a lot more expensive for reinforcement.

Maybe I'm being ignorant but why do you need a SAP analysis? You can size the wall on the back of a post it note using M = (1/6)(k0)(D^3) and do a simple drained/undrained SGBP and settlement calc. Deflection might be an issue if the internal faces of the walls are going to be clad with tiles or similar as these will obviously be more brittle than the walls.

Good luck! PS Don't think the client would be too impressed with a 2mm crack

 

[oldestguy]

Reviewing the above statements, it occurs t me that it may be worth the trouble to at least bounce the plan off an experienced pool contractor-designer. It would be a shame if some foreseen real problem develops later on and you find yourself in court or your reputation is ruined. There is nothing wrong with asking for comments (as you have here) from experienced persons. I think another source of advice is from those that build them, since they will want to be in on the action of doing the job. In addition to this forum, I would make a real effort to seek more advice. You could just get lucky and also you could just be very unlucky. In engineering and construction word gets around, especially not so good word.

 

[oldestguy]

I just did a look again above and see this statement.

"the site is in a mid-area between sea and mountain (average Mediterranean weather) but as you said, the soil is clayey expansive one for which we will do some treatment (strong compaction and base course fill underneath rafts)".

This tells me you REALLY need the advice of an experienced geotechnical engineer. Compacting expansive soil is probably the worst thing you can do where water later may be leaking to "feed" that expansive soil. This likely will be the downfall of this job if you follow through with that statement. The resulting picture won't be pretty.

 

[BUGGAR]

I trust you have considered flotation of the pool. There is nothing as awesome as seeing a large pool literally rise out of the ground. This beats Moses' parting of the sea.