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RE: SEISMIC: Design in Pakistan; General Questions

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The Ss is the short period earthquake at 0.2 sec.  The S1 is the long period earthquake at 1.0 second.  They are both predicated on the 2% in 50 year event.  There was a move to design to 2 probabilities a while back.  One for collapse and the 10/50 for non collapse issues.  It did not fly.  The 10/50 was used in the UBC and earlier NEHRP, but it did not provide a good margin for collapse for Eastern North American earthquakes. 

Regards, Harold Sprague


Date: Tue, 23 Feb 2010 16:21:24 -0500
From: bill(--nospam--at)
To: seaint(--nospam--at)
Subject: RE: SEISMIC: Design in Pakistan; General Questions

On February 23, 2010 at 4:09 PM Harold Sprague <spraguehope(--nospam--at)> wrote:

Regardless of the code, you need to ask yourself, what is good engineering practice?  I would be inclined to use as good of information as possible for the Ss and S1 and use the ASCE 7-05.  There are very good engineering reasons that the UBC-97 was superseded regardless of any jurisdiction having authority.
Harold, you're bolstering my own (internal) argument here, so no problem.
Can you answer me why they have TWO figures each for S1 and Ss in the UFC 3-310-01 publication? The "10/50" value of each is exactly 50% of the "normal" value. What is the significance?

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