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RE: Sloshing Damping

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OK. I'm busted. My ignorance is totally exposed. I am the reason the provision is evasive. We realized that there was no standard development organization (SDO) that addressed granular materials. We also knew that there was some point at which granular material may behave similarly to a fluid. The research is just not there. There is no SDO for granular material.

Most people design granular material storage facilities just for the impulsive and ignore the convective. I don't think anyone would argue with you if you took that approach especially with low seismic demand.

Harold Sprague

From: "Rich Lewis" <seaint04(--nospam--at)>
Reply-To: <seaint(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: RE: Sloshing Damping
Date: Wed, 22 Nov 2006 14:31:20 -0600

Thanks all for your response.

As you can tell from my question I'm a little confused.  I'm designing a
foundation for storage silos for plastic pellets. I'm in the lowest seismic zone so I don't think seismic will govern my design, but I want to check it.

ASCE 7-02 section is for elevated tanks for liquid and granular
material.  It says to design by an approved standard or by section 9.14.5.
The table for approved standards doesn't have a dry granular material
standard.  I'm looking at section 9.14.5 and it gives a seismic shear value
in equation What I'm wondering is how sloshing affects this value.
Will it increase it or decrease it.  What damping is included in this shear
value?  The commentary doesn't appear to address it.




From: William.Sherman(--nospam--at) [mailto:William.Sherman(--nospam--at)]
Sent: Tuesday, November 21, 2006 4:21 PM
To: seaint(--nospam--at)
Subject: RE: Sloshing Damping

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




From: Rich Lewis [mailto:seaint04(--nospam--at)]
Sent: Tuesday, November 21, 2006 3:07 PM
To: seaint(--nospam--at)
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?



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