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RE: Ordinary Truss Moment Frame

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I remember doing the same for previous projects, but to '94 UBC.  The same
approach, but a different set of parameters.  I would say the frame would
qualify as an OMF, as long as it's designed for R=4.5, and Omega loads as
you mentioned.  But, there could be others to argue otherwise.

David A. Topete, SE
Structural Engineer
 
GFDS Engineers
543 Howard St., First Floor
San Francisco, CA 94105
v : (415) 512-1301 x21
f : (415) 512-1302
dtopete(--nospam--at)gfdseng.com
www.gfdseng.com
 
-----Original Message-----
From: Gary Grinstead [mailto:Gary.Grinstead(--nospam--at)ci.stockton.ca.us] 
Sent: Wednesday, January 17, 2007 3:20 PM
To: SEAINT List Server
Subject: Ordinary Truss Moment Frame

I have several projects under review where the engineer is using an
Ordinary Moment Frame with trusses for the beam member.  The trusses
consist of WF top chord (single sided shear tab to column with no flange
connection), TS bottom chord, and TS webs (inverted V with a vertical at
midspan).  The connections have been designed for Omega loads (per CBC
2213.6.2).

The question I have is whether this is permitted by the code or must it
be a Special Truss Moment Frame?  Back when I started you'd see these
more frequently though I've usually seen open web joists were used for
the beams.  Since 1988, the UBC added a section regarding trusses in
SMRF and later added the category of Spectial Truss Moment Frame but is
silent regarding the use of trusses in ordinary moment frames.  What
I've found from online searches is also STMF only.  I don't know whether
this is because the extra requirements for Special Truss frames are not
required for Ordinary Truss frames the same way the requirements for
SMRF are not used for OMF.

All opinions will be welcome.





Gary Grinstead
Plancheck Engineer
City of Stockton
(209) 937-5097
Gary.Grinstead(--nospam--at)ci.stockton.ca.us

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