swimming pool wall design

[db7]

thread255-102015 Looking for guidance on design of shotcrete walls for swimming pools. Any references recommended? Also, it appears that the pool base is used to stabilize the overturnming moment from the walls. what effective length of the base is commonly used?

 

[hokie66]

The base of a swimming pool is continuous all the way across, so effective length doesn't come into it. The whole thing is a U-shaped concrete element.

 

[JAE]

The other thing about pool designs is that there are many pool contractors who use shotcrete and basically produce a 6 inch to 8" thick wall with rebar somewhat in the middle.

Their philosophy is that the pool wall forces (earth from the outside competing with the water on the inside) cancel each other out to a general degree such that the wall doesn't do much structurally.

What they don't take into account is that in some climates, pools must be emptied for winter. In warmer climates pools are emptied for maintenance, painting, etc.

The empty pool will have some level of lateral earth pressure develop on the wall. Depending on the backfill this pressure can develop rather quickly, or slowly.

Freezing of the backfill, if moist, can cause lateral displacements on the walls as well.

So that brings up the opposite philosophy of pool wall design: designing for all potential load combinations and earth pressures with empty pool conditions. You end up with thicker walls, but a more stable system. I just assisted a contractor who was widening some drain screens in a pool wall that was at least 18" thick for a 4 ft. depth.

 

[db7]

Thank you for the posts. I suspected the U-shaped design. With a concave wall shape it seems that this would produce some 3-D effects that would make a 2-D section analysis inaccurate. Any suggestions on how to model this?

Also, thanks for the comments on earth pressures. I do plan to design for the empty pool load case.

 

[JoshPlumSE]

Typically, the pool would be analyzed as a 2D retaining wall. We all know that it will receive some significant stiffening and load reduction due to the curving geometry of the pool. However, we would usually choose to ignore that. It's conservative to leave it out, right?

I have seen folks (Pool Engineering in Anaheim, CA) do some FEM analysis to account for the curved structure. But, most pools would not justify the extra engineering expense associated with this type of analysis.

 

[InDepth]

That is correct, pools are usually looked at as a 2D design, but based on the size and curvature of the pool you can take into account additional curvature. The issue isn't the analysis, but the quality control of the pool contractors.

Take a look at this link with standard plans.

http://www.pooleng.com/ca-27.aspx

 

[PEinc]

I agree with InDepth about quality control. A few years ago, I got a call from a pool contractor who was questioned by the code inspector about the pool's rebar placement. The contractor asked me to look at the partially finished pool and convince the inspector that the rebars were OK as already placed. After looking at and measuring the placement of the rebars and running some design calcs, I agreed with the inspector and the partially completed pool needed to be removed. The contractor was not very happy with me.

http://www.PeirceEngineering.com