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Re: Tension rod bracing

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Can Charlie or some one tell us WHY tension only systems are being so
restricted by the new codes? Is it something theoretical or performance
related ? After all, we have lived with them for so long.

S A Masroor

----- Original Message -----
From: "Harold Sprague" <spraguehope(--nospam--at)hotmail.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, June 15, 2006 11:26 PM
Subject: RE: Tension rod bracing


> What you stated is true.   I was presuming that Drew was wanting to remove
> an SCBF and replacing it with a tension only OCBF.  But tension only
OCBF's
> are are very restricted more by the IBC and ASCE 7 as opposed to AISC.
The
> original concept (crafted in the secret code development room on a far
away
> planet) was to just allow tension only OCBF's for PEMB's only for
buildings.
>
> Obviously, there are more variables that need attention.  But the
> fundamental question of using a tension only OCBF is that they are allowed
> under some limited circumstances.  Some of the best performing structures
> around are the tension only braced systems used for elevated water towers.
> Now these are important structures, and they have a good track record.
> Granted they do some special features, but the basic concept is still a
> tension only OCBF.  By the way, we allow tension only OCBF's if they are
> categorzed as nonbuilding structures.
>
> Regards,
> Harold Sprague
>
>
> >From: "Haan, Scott M POA" <Scott.M.Haan(--nospam--at)poa02.usace.army.mil>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: <seaint(--nospam--at)seaint.org>
> >Subject: RE: Tension rod bracing
> >Date: Thu, 15 Jun 2006 07:12:48 -0800
> >
> >You cannot have a specially concentric braced frame with tension only
> >bracing
> >without any compression bracing per AISC341-02 13.2c.  The exception to
the
> >30% to 70% tension brace rule says you need to have some compression
braces
> >designed for special load combinations in any line of bracing if you
> >violate
> >the 70% amount of tension braces.
> >
> >If you are going to have tension for a grid line they need to be designed
> >for
> >special load combinations with an ordinary braced frame R.
> >
> >-----Original Message-----
> >From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com]
> >Sent: Wednesday, June 14, 2006 4:21 PM
> >To: seaint(--nospam--at)seaint.org
> >Subject: RE: Tension rod bracing
> >
> >As with everything else.... it depends.  Are you using ASCE 7 or IBC, and
> >which edition?
> >
> >The 2002 AISC Seismic Provisions do not preclude tension rod bracing.
What
> >will limit the applicability is the ASCE 7 or IBC.  The biggest variables
> >are:
> >A.  Seismic Design Category.  Since you are using a SCBF, I would presume
> >that you are in SDC D, E or F.
> >B.  Height
> >
> >Look at ASCE 7-05 Table 12.2-1.
> >
> >Regards,
> >Harold Sprague
> >
> >
> >
> >
> >
> > >From: Drew Morris <dmorris(--nospam--at)bbfm.com>
> > >Reply-To: <seaint(--nospam--at)seaint.org>
> > >To: SEAINT <seaint(--nospam--at)seaint.org>
> > >Subject: Tension rod bracing
> > >Date: Tue, 13 Jun 2006 09:18:26 -0800
> > >
> > >Under the 2002 AISC Seismic Provisions is tension rod bracing
prohibited?
> > >We have a case where the building will be designed as a special
> > >concentric braced frame, but the architect is objecting to those braces
> > >that will be in front of large windows.  Can tension rod bracing be
> > >used for these locations?  The building is a 2 story structure and the
> > >braces will be on both levels.
> > >
> >
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