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RE: ASCE 7-98

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Ss, S1, Sds, Sd1, etc. are really acceleration parameters (rather than
true accelerations).  Ss and S1 are equal to the mapped values divided
by 100%g.  For instance, a point on Figure 9.4.1.1 (a) that shows
163%g indicates that Ss=1.63.

Soft soils amplify weak shaking more than strong shaking.  Soft soils
may deamplify very strong shaking (thus Fa < 1 in some cases).

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Michael Valley, P.E., S.E.                   E-mail: mtv(--nospam--at)skilling.com
Skilling Ward Magnusson Barkshire Inc.              Tel:(206)292-1200
1301 Fifth Ave, #3200,  Seattle  WA 98101-2699      Fax:        -1201

-----Original Message-----
From: Padmanabhan Rajendran [mailto:rakamaka(--nospam--at)yahoo.com]
Sent: Monday, May 14, 2001 11:26 AM
To: seaint(--nospam--at)seaint.org
Subject: ASCE 7-98


In ASCE 7-98, what is the unit of {S sub S} (mapped
maximum considered earthquake spectral response
acceleration? Is it equal to the value from the map
times 32.2 ft per second squared?

In Table 9.4.1.2.4a, I note that, for a given site
class, {F sub a}reduces with {S sub S}. What is the
explanation?

Thanks.
Rajendran


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