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Re: Concrete below base

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-----Original Message-----
From: jwalsh(--nospam--at)saii.com <jwalsh(--nospam--at)saii.com>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Thursday, August 26, 1999 5:55 PM
Subject: Concrete below base


>We are designing a steel special concentric braced frame, 3 stories, in
seismic
>zone 4 with rectangular concrete footings below the braced bays.  Section
>1921.2.2.3

Says members which transmit seismic forces " to the foundation".  It is
seldom possible or desirable to mobilize ductility in foundations. Not
possible due to proportions, not desirable since cracking and yielding is
not visible nor repairable. Thus foundations should instead be designed on
the basis of probable capacity of the members delivering forces, or other
limiting factors, perhaps stability overturning/rocking behavior, etc.