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RE: UBC R factor for braced frames

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The reason for the low R is the tension only (non-ductile) brace. If you use
a regular braced frame, you should at least be able to use R=4.4, which is
allowed for braces carrying gravity loads. It's one of those things that
proves codes cannot predict every possible scenario and one needs to apply
some good ole engineering judgment when using any code.

Ben Yousefi, SE
San Jose, CA

-----Original Message-----
From: Ed Tornberg [mailto:edt(--nospam--at)blazerind.com]
Sent: Tuesday, November 12, 2002 7:12 AM
To: seaint(--nospam--at)seaint.org
Subject: UBC R factor for braced frames


Light gauge steel, bearing walls, tension-only bracing requires R = 2.8.

1.  Does anyone know why this is less than steel braced frames where
bracing carries gravity load?
2.  If I install the braced frame in a light gauge steel stud bearing
wall, but the vertical bracing members do not carry gravity load
(adjacent studs do), to the extent that the building cannot collapse due
to gravity loads if the braced frame fails, can I use a higher R factor,
such as for a building frame system?  

Thanks,
Ed


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