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Re: Link in Columns

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First, to reply to your question:  The term LINK, in my understanding, is
the area of concentrated moment and shear that is intended to deform
inelastically thereby dissipating energy while the balance of the frame
remains essentially elastic.  It is essential that the link remain ductile
and stable for overall frame rigidity.  LINKS are used in eccentrically
braced frame systems.
The reason I say DO NOT place a link in a column is because the absolute
last place you want to purposefully introduce a plastic hinge is in a
column, regardless of whether the code would permit such a thing.
Deliberately introducing a point of inelastic rotation in a column element
invites collapse.

OK, you describe using a half-height chevron brace, basically a knee brace
at the lower level. If by LINK you mean simply the brace connection, this is
still not something I would approach favorably.  You are introducing a large
horizontal reaction at the mid-height of the column.  In my mind this is
worse than the aforementioned K brace, as you must rely entirely on the
internal restoring forces within the column.  Without looking for code
sections at the moment, I would seriously doubt this is permitted for
anything except miscellaneous structures, trellis elements, and the like.

Look carefully at the P-delta implications, and the possibility of inelastic
overload.

Paul Feather
San Diego, CA


----- Original Message -----
From: "Joseph Harouni" <yosi_h(--nospam--at)msn.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, June 04, 2001 4:48 PM
Subject: RE: Link in Columns


> I am actually using Inverted V brace frame, that the bottom of the brace
> connection is 8 feet above base (foundation), in a 2 story building with
2nd
> floor 16 feet above base and roof 18 feet above the 2nd level (this upper
> level has cross bracing). You mentioned " DO NOT place the link in the
> column" any reason for that?
> Thanks,
> Joseph Harouni
>
> -----Original Message-----
> From: Paul Feather [mailto:pfeather(--nospam--at)san.rr.com]
> Sent: Monday, June 04, 2001 1:22 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Link in Columns
>
>
> Are you referring to a K brace?  if so, there is limited acceptability in
> the code for K braces in zone 4, but I do not know a single engineer who
> would actually use this configuration.  Historically this type of braced
> frame has performed very poorly.
> If you use a K brace there are very strict requirements for column
> performance that in essence will make this option particularly
> un-economical.
>
> If you are asking about links in terms of eccentric braced frames, DO NOT
> place the link in the column.
>
> Paul Feather
> San Diego, CA
> ----- Original Message -----
> From: "Joseph Harouni" <yosi_h(--nospam--at)msn.com>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Monday, June 04, 2001 10:38 AM
> Subject: Link in Columns
>
>
> > Hi,
> > Does code allow design of LINKs in columns vs. in beams when designing
in
> > zone 4 based on Seismic Provisions (which essentially is an inverted V
> brace
> > (Chevron Brace) or Knee Brace)?
> > Thanks,
> > Joseph Harouni
> >
> >
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