Pool Design
Pool Design
(OP)
Why is there so much variance in pool design?
I have had 2 engineers design a reinforced concrete above ground pool.
Design 1 - 250 thick shell N16-300 each way on both faces of the pool shell
Design 2 - 220 thick shell S12-200 each way on both faces of the pool shell
Now the guys constructing the pool claim that they have never seen so much steel go into a pool and want to get another engineer to carry out a further design.
Surely its not rocket science.
Is there a book or reference available with standard pool calculations/examples?
I have had 2 engineers design a reinforced concrete above ground pool.
Design 1 - 250 thick shell N16-300 each way on both faces of the pool shell
Design 2 - 220 thick shell S12-200 each way on both faces of the pool shell
Now the guys constructing the pool claim that they have never seen so much steel go into a pool and want to get another engineer to carry out a further design.
Surely its not rocket science.
Is there a book or reference available with standard pool calculations/examples?






RE: Pool Design
"Above ground" is all you have told us about the pool. Your pool builders are probably used to building in ground pools, which typically require less reinforcement.
Using N16 bars suggests the pool has essentially square corners, while using S12 bars suggests a freeform pool. Which is it?
RE: Pool Design
1) Several load cases for filled/unfilled etc.
2) Heavily dependent on serviceability issues (crack width etc) that aren't code defined.
3) The free-form pools that Hokie mentioned can require pretty complex analyses.
4) It's a high value item with high potential for liability. Rebar and concrete are cheap in comparison.
Most of the pools that I've dealt with have actually been designed by specialty pool consultants. So yeah, maybe a bit like rocket science.
There's plenty of reference material for the non-structural aspects of pools but next to nothing for the structural design as far as I can tell. I've found one page worth in one book on retaining walls: Link. I have the 8th edition.
There's plenty of information on containment tanks but that's a whole different animal.
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.
RE: Pool Design
The pool is square (8m X 4m), 1.8m deep at the deep end and 1.2m deep at shallow end with steps along the short edge at the shallow end. Base will be sitting on rock foundation and the rest of the pool will be above ground
The design does not concern me really - the cost will be the cost and the client pays.
Its just the pool contractors are jumping up and down saying that there is too much steel and concrete - they claim that they have built pools like this before using S12-300 with 180 thick shell - in complete contrast to the 2 engineer designs.
Yes I will always take an engineers advice over some contractor, but was just curious as to if there was reference book available with standard pool calculations/examples to review.
Are the engineers being too conservative or is it the typical story of the contractors using its the way we always do it scenario?
RE: Pool Design
Why did you have 2 engineers design the same thing? Do they know that? It would aggravate me, and I might choose not to work with you in the future.
This is a water retaining structure, and the reinforcement is a bit light on for my liking. So there, you have another opinion for free.
RE: Pool Design
RE: Pool Design
1) Mrs. Contractor: can you supply examples of similar, engineered projects that were substantially different?
2) Mr. Engineer(s): is there anything exceptional about this project that would have impacted the design?
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.
RE: Pool Design
It's difficult to get the idea across sometimes that something may not fail, but can still be inadequate in design.
RE: Pool Design
RE: Pool Design
Then they fill it with water and the idea is that the water lateral force and the earth lateral force sort of match each other and the pool concrete wall isn't really serving as a structural wall.
The problem with this is that if you ever empty the pool (say in northern climates where you don't want frozen water in the winter) you might get a collapse.
So the right way to design a pool is with a cantilevered wall system with minimum required reinforcement appropriate for water bearing systems (in the US we use ACI 350 which requires higher reinforcement than in non-water bearing systems).
I think you contractors are used to building undesigned and minimalistic tanks.
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RE: Pool Design
The most important thing is crack control. Depending on where you are located, the provisions vary a bit, but I want 0.5 to 0.6% Ag reinforcement. This amount is necessary to control restraint cracking, first in the floor due to restraint by the rock, then in the walls due to restraint by the floor.
Design 1 above has 0.53% Ag, and Design 2 has 0.50% Ag, so these designs are not far off the mark.
RE: Pool Design
So I would say the two designs you've received from engineer's are pretty well on the mark.
RE: Pool Design
Then when a problem occurs the statement gets shortened to "I'm not an Engineer."
RE: Pool Design
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Pool Design
RE: Pool Design
nearly every time I have let a contractor talk me into doing it a different way it was
a) a way for the contractor to save a lot of money (not much for the owner though) and
b) a mistake because the quality went down or
c) the contractor had no idea what he was doing and it was fubar
RE: Pool Design
May be a stretch, but that is just my opinion.
Mike McCann, PE, SE (WA)
RE: Pool Design
Mike, not all countries in the world require engineers to be licensed, and the OP appears to NOT be in the USA given the use of terms of N16 and S12 rebar designations, coupled with metric units, and I hazard a guess that the OP may be in Australia.