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Re: Sloshing Damping

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There are many good references out there on the simplifications API and AWWA make for tank analysis. Google for such names as Lydik Jacobsen (sp?), George Housner, Medhat Haroun among others.  They describe the theory and give you a feeling for the "code" equations in AWWA or API.
Regards,
Bill Cain, S.E.
Berkeley CA
 
In a message dated 11/22/2006 5:30:35 A.M. Pacific Standard Time, fugeeo(--nospam--at)gmail.com writes:
I did some sloshing calcs before too, using AWWA or APWWA ( I am not sure of the acronym Water Association ) equations.  Straight forward, but complicated.
For Damping, I don't know, I think your best bet might be to model the whole water as a block of material, providing additional thrust mass (or modeled in the density) due to the water.  Maybe using the water with very very small shear stiffness in a 3-D element.  Then, run the static analysis.  Find the reactions at the tank, then put in an equivalent spriing/damper at the location of the tank using your 0.5% damping.

Maybe this will give you ideas.

On 11/22/06, Syed A Masroor <masroor(--nospam--at)eaworld.com> wrote:
There is nothing secretive about this. The formulae and graphs are documented in API codes. The forces are much reduced for large shallow tanks. 
----- Original Message -----
Sent: Wednesday, November 22, 2006 4:29 AM
Subject: RE: Sloshing Damping

I did several tank seismic calculations in the past using some complicated formulas developed by the petroleum industry to take sloshing into account.  In most cases it reduced the overall lateral force, but in some increased it from that of the 5% damped levels.  I don't know if any of these formulas are available for use beyond the petroleum industry however.  They were kind of secretive about them.

William.Sherman(--nospam--at)CH2M.com wrote:
It doesn't reduce your seismic shear.  Normally acceleration response spectra is based on 5% damping for buildings.  For sloshing water, the damping is reduced to 0.5%, which in turn increases the spectral response. The response at 0.5% damping is 1.50 times that at 5% damping.
 
Bill Sherman
CH2M HILL / DEN
720-286-2792
 


From: Rich Lewis [mailto:seaint04(--nospam--at)lewisengineering.com]
Sent: Tuesday, November 21, 2006 3:07 PM
To: seaint(--nospam--at)seaint.org
Subject: Sloshing Damping

ASCE 7 allows for 0.5% damping for sloshing of material in a storage tank.  How do I use this number to reduce the seismic shear?
 
Thanks.
 
Rich
 



Mark Pemberton, S.E.

Pemberton Engineering
502 Mace Blvd., Suite 2B
Davis, CA 95616

Ph:  (530) 792-0511
Fax: (530) 792-7109

 
Regards,
Bill Cain, S.E.
Berkeley CA