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Re: braced frame gusset plates

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Eli,

You will find good engineering and detailing background in two STEEL TIPS publications from the Structural Steel Education Council:

1.  Design of Special Concentric Braced Frames, May 2004

2.  Seismic Behavior and Design of Gusset Plates, December 1998

Thomas Hunt, S.E.
ABS Consulting




"Eli Grassley" <elig(--nospam--at)psm-engineers.com>

10/12/2004 10:07 AM

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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
PETERSON, STREHLE, MARTINSON, INC.
SEATTLE, WA