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Re: Seismic acceleration of H2O

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(This message is being re-sent since it didn't appear to go thru the first
time.)

In general, current seismic design procedures for fluid containments are
based
on the Housner method (described in Chapter 6 of TID-7024, National
Technical
Information Service, US Department of Commerce).  This includes
considerations
for portions of the fluid as sloshing (convective mode) and as fixed
(impulsive mode).  The American Water Works Association has similar seismic
design procedures for Welded Steel Tanks for Water Storage in their
publication ANSI/AWWA D100-96.  Committee 350 of the American Concrete
Institute is working on a new code for Environmental Engineering Concrete
Structures, ACI 350, which will include Chapters 21 & 52 on Seismic Design
of
Liquid-Containing Structures - but it has not been published yet.  The codes
are being written in the format of current U.S. building codes but with
reduced "ductility" factors (e.g., Rw = 2.75 would correspond to designing
the
tank for ground acceleration with Cmax = 2.75).

Conservatively, the entire fluid contents can be assumed as accelerating as
a
mass (impulsive mode), with the fluid force applied 1/2 on each the front
and
back walls (for a rectangular tank with cantilevered walls) and with
resultant
load at mid-height of fluid.  This can be used for small tanks but would be
too conservative for larger tanks.