UBC Section 1632.1, 2nd Paragraph
" Attachments shall include anchorages and required bracing. FRICTION RESULTING FROM GRAVITY LOADS SHALL NOT BE CONSIDERED TO PROVIDE RESISTANCE TO SEISMIC FORCES".
So as long as you are clamping by use of pre-tension or other gripping method, you are okay as long as you neglect the dead weight of the mass you're trying to stabilize when determining the level of resistance.
Hope that helps,
>>> rlabbe(--nospam--at)ctcinternet.cl 04/24/01 08:36PM >>>
Thanks for your information. It's very clear.
Anyway I don't see any reference to a specific
code dealing with this.
De: Mike Valley <mtv(--nospam--at)skilling.com>
Para: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Fecha: Martes, 24 de Abril de 2001 11:51 a.m.
Asunto: RE: Earthquake counteracted by friction?
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.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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
From: raul labbe [mailto:rlabbe(--nospam--at)ctcinternet.cl]
Sent: Monday, April 23, 2001 10:55 PM
Subject: Earthquake counteracted by friction?
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
In the jungle of the american codes, is there anyone,addressing this
issue ? and what do their provisions specify ?
S. S. Eng. Raul Labbé
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