RE: Seismic response

From: <Conner>
Date: Tue Oct 04 2005 - 10:04:00 EDT

Christopher Wright wrote:

<<<...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…>>>

Some might be interested in reading the account I happened to notice yesterday at the site
http://www.alyeska-pipe.com/Inthenews/techpapers/3-TAPS%20AboveGround%20Denali%2\ 0EQ.pdf that includes some detail of the design of a critical area of the Alaska Pipeline, I think probably more than 30 years ago, and a subsequent very severe testing of this pipeline and design at this location a quarter of a century later in the magnitude 7.9 Denali earthquake of 2002. I understand a major fault in the area of this crossing underwent several meters of ground movement during the earthquake event described in many places including http://www.aeic.alaska.edu/Seis/Denali_Fault_2002/. Per the latter site, this is the largest earthquake to hit North America in 150 years. I noticed per "Figure 5" of the former report that reportedly this event involved a "Spectral Acceleration, g" of about 1.0 (or a little more) at a Frequency, Hz of 1.0 (or a little more), and near fault ground movement was described in another area of the former report as "violent". There was reportedly no loss of pipeline contents, the pictured damage to some support members was repaired in only 66 hours following the event, and the pipeline was then put back in operation .

[This was of some interest to me in that while I think some folks from Japan furnished the carrier pipe, I know our American Steel Pipe division furnished significant other piping material for 78,000 (most if not all) of the Vertical Support Members for this massive pipeline project.]

Randy Conner
Research Department - Technical Division American Cast Iron Pipe Company
1501 31st Avenue North, Birmingham, AL 35207 P. O. Box 2727, Birmingham, AL 35202
ph 205-325-7946
fax 205-325-8095

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