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Swimming Pools

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Nels,

I always recommend that a person contact a swimming pool company for a 
residential pool and explain that the pool company can amortize the 
engineering cost over many pools, but the engineering cost for one pool has 
to be borne by the owner.  If a pool has a "free-edge," or is bordered with 
a retaining wall, I will design a retaining wall for the pool, consider the 
soil behind the wall fully saturated, put many weep holes in the wall, but 
will not design the pool.  

A number of years ago, I got a frantic call from a contractor for an upscale 
resort/development that was still under construction that a retaining wall 
"just went south" as a result of a swimming pool leaking.  I wasn't able to 
get out to look at it and referred them to another engineer, but did ask them 
if the retaining wall had weep holes and if water had been coming out of the 
weep holes.  "Like Vesuvius," I was told.  Construction workers have very apt 
ways of describing things! 

It seems that most free-form pools function more as a shell than as flexural 
members, however, a rectangular pool would seem to behave flexurally, more 
than as a shell.  

Good luck.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Nels Roselund wrote:

>>I have a project for renovation of a historic residence that  includes a new
swimming pool on the grounds.  It is to be a square-cornered pool that will
be finished on the inside walls and bottom with a tile mosaic.  It will be
constructed into an excavation into soil.

Where can I find structural criteria for design of this kind of structure?
What kind of recommendations should I request of the soils engineer?

I've got a copy of ACI 350R-89 Environmental Engineering Concrete Structures
that appears to have appropriate guidelines including crack control,
corrosion control imperviousness.  Are the criteria in ACI 350 appropriate
for a swimming pool?

I also have The PCA publication "Rectangular Concrete Tanks", 1998 edition
that seems to provide the factors needed to evaluate the moments and shears
in the walls and bottom of the structure.

I visualize designing the empty pool as a tank structure retaining
inward-acting active earth pressure or flooded backfill.  Outward pressure
is less clear -- the walls will be confined by passive soil pressure, which
will reduce the net outward pressure, but the relative rigidities of soil
and tank walls would need to be evaluated in order to determine the net
outward pressure -- is that what is done?<<