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# RE: App weight of steel tank

• To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
• Subject: RE: App weight of steel tank
• From: "Lutz, James" <James.Lutz(--nospam--at)earthtech.com>
• Date: Fri, 25 Mar 2005 09:04:06 -0800

```I will give you the same answer I give everybody else. "It depends."

The gravity loads transferred to the foundation at the interior and
perimeter of the tank will depend on whether it is a mat or a ringwall
foundation, and whether or not there are interior columns. I would guess for
a tank of these dimensions you might have a self supporting dome roof, in
which case all the roof weight, snow load, are distributed at the perimeter.
For a tank this tall, you would probably be using higher strength steel in
the bottom courses to keep the plate thickness down.

For a quick and dirty gross dry weight estimate for preliminary purposes,
estimate the thickness of the shell at the bottom based on water pressure at
the base and an allowable hoop stress of 15 ksi and round up to closest
1/16". Assume shell thickness at the top of 1/4" and add an allowance to the
shell height for freeboard. This can be several feet if you are in a high
seismic area. Compute the shell weight based on the average thickness. For
the roof, figure maybe 10 to 20 psf, depending on framing, configuration,
appurtenances, etc. Tank floor figure 1/4".

Wind loads on the tank when empty will create up and down loads at the
perimeter, and if you are in seismic area, the foundation loads will be
appreciable and probably require anchorage. If you have a mat rather than a
ring wall foundation, you will also have to include seismic overturning
moment associated with differential pressure on the mat caused by the
profile of the water surface, which goes up on one side and down on the
other when the tank sloshes. It's not all that simple. Do you have access to
AWWA D100 or API 650? These are the design standards for water and oil
tanks. If you are in a jurisdiction that uses IBC2003, which references ASCE
7-02, you will have to modify the AWWA or API formulas.

-----Original Message-----
From: Nat Mohanram [mailto:nattamaim(--nospam--at)yahoo.com]
Sent: Friday, March 25, 2005 6:43 AM
To: seaint(--nospam--at)seaint.org
Subject: App weight of steel tank

Can any one help me to guess approximate weight of
steel tank for storing water , 90 fett dia and 90 ft
tall.
I have to design preliminary foundation.

Thanks

Nat

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