Re: Seismic response of hydraulic oil tank

On Oct 3, 2005, at 4:34 AM, Steve McKenzie wrote:

> Question 1: does anyone have a reputable calculation reference for
> the natural (slosh) frequency of a rectangular tank with known
> dimensions, fill depth fluid density and viscosity?
The classic calculation is by Housner 'Dynamic Pressures on Accelerated Fluid containers,' Bulletin Seismological Society of America, 47(1) Jan 57. I expect it's been re-printed in a dozen different textbooks and references. Mine is _Nuclear Reactors and Earthquakes_ US Atomic Energy Commission TID-7024, which you may be able to get. Otherwise try to Google out G. W. Housner.

> It appears to me that unless the vibration spectrum is
> known, it is not possible to calculate the stresses in the tank walls.
I think those accelerations you have are the spectral accelerations. A ground acceleration greater than 1 G would destroy everything totally. A magnitude 8 quake only has epicentral accelerations of 1-2 g. I think what you need to do is figure the structural frequencies and apply the given accelerations as if they were static loads. Even those are very high for spectral accelerations. I got a set of response spectra for Taiwan with peak values up around 12G, and I think someone is worst-casing himself into an early grave. A 2g ZPA would destroy the island. None of the half-dozen or so survivors would give a damn if an oil tank were the only thing left standing on the whole island. But that's what they claim they wanted…

Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania