Oil Tank Seismic Design

[PMR06]

I'm asking this to mediate a discussion (argument) in our office regarding seismic design force on an oil tank and supporting structure. We are to design the foundation and supporting structure for the tank, not the tank. Here's the setup: (please forgive my QWERTY CAD)

____________________________
/ \
| 160 kip tank |
\____________________________/
| | | |
___|_|________________|_|____
|____________________________|


This is located in Zone 4 California (CBC 2001 code). The tank is 10ft diameter, 30ft long and the bottom of tank has to be 5ft above grade. It is supported by reinforced concrete walls at each end which are on a mat foundation.

Are the foundation and stem walls designed for Fp (force on component) or V (base shear under "Non Building Structures")? Fp is about 10x V! If using Fp, checking OTM works, but in order to get that magnitude a force into the ground we need a really deep mat or drilled piers.

Any thoughts? Thanks in advance.

 

[Bagman2524]

I think you need to use Fp. Why is Fp 10 x greater than V. Seems your support structure may be too flexible.? I would suggest a stiffer support structure to reduce Fp.

 

[OldPaperMaker]

PMRO6,
Since 1-1-08 California follows the new CBC (08?) which follows the 2006 IBC and uses ASCE7-05. Therefore, you will probably have to use ASCE 7-05,Chapter 15, "Seismic Design Requirements for Nonbuilding Structures" to determine the design loads. "Complicated" is probably a gross understatement
There is no "zone 4" in ASCE 7. You will have to get the site latitude & longit. and go to the USGS web site to get the Sds & Sd1 values.
Good Luck!

 

[IFRs]

http://earthquake.usgs.gov/research/hazmaps/design/download.php