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RE: truss bracing

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Bot chord of trusses are usually in tension unless wind uplift is high enough to generate compression in them, in which case bracing is required. Does the mezzanine structure itself provide for any bracing? It seems it may be adding enough dead load to reduce any possible uplift.
 
Ghassem
-----Original Message-----
From: Mark D. Baker [mailto:shake4bake(--nospam--at)earthlink.net]
Sent: Thursday, December 07, 2000 9:50 AM
To: seaint(--nospam--at)seaint.org
Subject: truss bracing

I'm working on a 1930's era commercial building with the following condition.
 
Arch trusses spanning 45'. Truss height is 7'-8" at apex of arch. Spacing between trusses is 15.5'. There are 6 truss bays.
 
Bottom chord of trusses were originally braced at midspan with a rough sawn 2x6 running horizontally, truss to truss, and rough sawn 2x6 in cross brace fashion running bottom chord of one truss to top chord of next truss.
 
At some point in time a mezzanine was constructed and the builder removed the cross bracing so it wouldn't be in the way of people walking on the mezzanine. This occurs in two truss bays.
 
What criteria is there for bracing the bottom chord of these trusses. At the two bays in which bracing needs to be replaced I would like to keep as much mezzanine area unobstructed as possible. Bracing at third points pretty much destroys the mezzanine space. I've thought of bracing from the mezz. floor to the bott. chord of truss. Anyone have a reason not to do this?
 
All thoughts will be appreciated.
 
Thanks,
 
Mark