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RE: Determination of Seismic Performance Category for a Specific Site

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I don't think that you have all the information to answer the question yet.
And you have 2 distinct problems.

The first problem is that the 1997 UBC has a bit of a problem with
compatibility.  The traditional UBC seismic zones are what defines seismic
pseudo static forces in Chapter 16.  The 1997 UBC steel seismic Chapter 22,
Division IV was written by the AISC and generally uses the coefficients (Av
& Aa) derived from the FEMA 222A & FEMA 223A.

The second problem is definition of the site seismicity.  I don't know what
the "basic seismic acceleration of the site" means.  I think that you are
still talking about seismic coefficients.

To get to a proper solution, I would get a copy of the FEMA 222A & the FEMA
223A from the Federal Emergency Management Agency in Washington, D.C.  The
commentary explains the relationship of the Aa and Av to other seismic
parameters.

Not knowing the exact site in China, I would speculate that the 0.1 is a
coefficient similar to the Z factor in the UBC it is also similar to the Av
factor in the FEMA 222A.  By these accounts, this would indicate a low
seismic risk zone.  It will probably not drive the primary lateral load
force resisting system, but can govern for components such as the condensate
tank, turbines, and other large mass equipment.

Regards,
Harold Sprague, P.E.
The Neenan Company
harold.sprague(--nospam--at)neenan.com


-----Original Message-----
From: Zhang, Zhigang [mailto:ZZHANG(--nospam--at)MitsuiBabcock.com]
Sent: Monday, February 01, 1999 1:56 AM
To: 'Seaint'
Cc: Khabbazan, Mehdi; Bhatti, Sohan S
Subject: Determination of Seismic Performance Category for a Specific
Site


Dear Sirs,

We are a British Company, "Mitsui Babcock", currently involved in the design
of a power station in China. The seismic design of the project should be in
accordance with UBC 97 according to the Client's requirements and the basic
seismic acceleration of the site has been reported as being equal to 0.1g.
According to UBC 97, there are four categories for structures based on which
the necessary seismic provisions are decided. In order to determine a
category, according to Table 2-2 of Chapter 22, Div IV, the Effective Peak
Velocity-Related Acceleration, Av, for the site under consideration is
required.

We would appreciate your comments on the following points regarding the
above:
1). Can the value of Av be decided by using the value of the site design
acceleration?
2). If the answer to question 1) is No, what relationship we should use to
obtain Av value?

Your assistance is highly appreciated.

Zhigang Zhang