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Re: Sloshing

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I do somewhat agree with you as well as Bill about the ACI 350.

In a swimming pool there would be two conditions when the pool is empty, the structural component would be similar to retaining walls when the pool is full of water, the resultant force would be applicable depending upon the seismic effect. i.e. pool design may govern based on the seismic design of retaing walls.
(the empty condition may or may not be the case when earthquake occurs)

If the tank is above grade then the condition would be different just as you specify.

I have numerous publications (research papers and reports) covering  these subjects which the ACI Committee 350 is unaware of i.e. not cited in the refernces). 

There is a PCA publication based on the ACI 350. 

EERC library holds several publications. Two publications I have are based on the tankon graound and tank on ground and tower design. Unfortunately these two publications are in SI System and one is in French. These two publications does cover a design examples


>>> Jim.Lutz(--nospam--at) 02/27/07 11:44 AM >>>
I wouldn't think you would normally be too concerned about sloshing
effects for something like a swimming pool, particularly if it's a
typical in-ground installation. If it is inside a building, that's
another matter. If you wanted to prevent spillage from a sloshing wave
in an earthquake, the freeboard requirement might put the water level
enough below the deck that your client would be unhappy with the loss of
function and appearance. The magnitude of the wave will also depend on
the ground motion you are dealing with, and if you are talking about
something like a swimming pool on top of a building, the amplification
effects of the structure. 

You should always check for dynamic effects and the increased water
pressure for safety, but you will probably find that service level
stresses and crack control requirements govern the design. For cisterns
with lids, I would definitely go through the exercise of computing the
sloshing wave height and making sure you have adequate freeboard. The
usual design formulas are predicated on a free water surface. As soon as
a sloshing wave contacts the roof of a tank, the assumption is no longer
valid, and you have a trapped momentum problem that can lead to sizable
increases in seismic base shear, pressure surcharges and vacuums in the

I would second Bill Sherman's remarks about the applicability of ACI

Jim Lutz, P.E., S.E.

720 3rd Avenue, Suite 1200
Seattle, WA 98104-1820
206 505 3400 Ext 126
206 505 3406 (Fax)

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