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RE: Earthquake counteracted by friction?

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U.S. practice does not permit the use of seismic resistance based on friction resulting from gravity loads.  However, friction resulting from structural action (preloaded bolts, for instance) is permitted to be considered when calculating seismic resistance.
 

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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: raul labbe [mailto:rlabbe(--nospam--at)ctcinternet.cl]
Sent: Monday, April 23, 2001 10:55 PM
To: seaint(--nospam--at)seaint.org
Subject: Earthquake counteracted by friction?

Fellow Engineers,
 
I will appreciate information regarding the following issue :
 
In an X industrial project,we required the installation of tall
vessels, whose anchoring system,according to the vendor's
drawings,( american vendor ) included only the bolts. We claimed
for the addition of the corresponding shear keys, to take account
of the horizontal seismic thrust, ( high seismicity area ). But the
answer was that they were not using shear keys, because it was
enough to provide an initial preload to the bolts. The shear force is
supposed to be counteracted by the friction between the base ring
and the foundation.( Friction is improved by the preload ).
 
In my country,the codes do not allow to rely on friction, regarding 
sesimic loads, but no reference is made for the case of 'prestressed 
anchor bolts'.
In the jungle of the american codes, is there anyone,addressing this
issue ? and what do their provisions specify ?
 
Regards,
 
S. S. Eng. Raul Labbé