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RE: braced frame gusset plates

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Commentary C13 (page 116) of the 2002 AISC Seismic Provisions has some info on this.  Also, don't forget to add crushable foam on the sides of the gusset plates where they are restrained by a concrete floor slab that extends into the 2t region.  This will facilitate buckling.  That's all I got.
Bob G.
-----Original Message-----
From: Eli Grassley [mailto:elig(--nospam--at)]
Sent: Tuesday, October 12, 2004 10:08 AM
To: seaint(--nospam--at)
Subject: braced frame gusset plates

List -

I've been updating all of my concentric braced frame connection details as I get new 2003 IBC jobs across my desk.  I've been trying to incorporate all of the latest AISC 2002 seismic provisions into my details...most notably the 2t "fold line" that is supposed to give the gusset some ductility to yield out-of-plane.  My question is on some other recommended dimensional details:


* I saw somewhere, a design seminar I believe, where it was recommended to chop the end off the gusset where it connects to the brace so that the gusset end is square (90 deg. relative to the brace line...i.e. don't bring the brace into the pointed end of a rectangular gusset plate).  And also that a dimension of 1" to 2" of the gusset plate should provided on either side of the brace...providing a "margin" for welding the brace to the gusset I would assume.


* Further detailing I have seen (dreamt up?) is that the sides of the gusset that extend away from the brace back to the beam/column should "flare out" away from the brace at a minimum angle of 30 degrees.  I suppose this would have the effect of spreading out the compression force from the brace and increasing the likelihood of a ductile compression failure.


Can anyone comment on these detailing tweaks?  I'm sure they would provide for better gusset performance, but they also add a lot more material and fabrication complexity to the cost of the gussets.  Is there a Modern Steel article that talks about "state of the art" gusset plate detailing that anyone is aware of...Charlie, maybe you could add some insight to this??


Thanks for any input.



Eli S. Grassley




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