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RE: metal bld'g. cable cross bracing

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Mark,
 
Not sure what you are asking here...  roof bracing typically transfers the longitudinal (perpendicular to the frames) loads from the middle of the building (assuming symmetric building) to the sidewall bracing rods with the roof beams and columns acting like struts.  I don't see the uniqueness here... how else other than diaphragm action would you get the longitudinal loads in the middle of the building out to the sidewall braces (weak-axis bending resistance of a long roof beam would be incredibly low)? 
 
Roof bracing could also be used to transfer lateral (parallel to the frames) loads from one frame to another frame or support.  You might typically see this when a pinned frame is used at a building endwall that has too many openings for endwall rod bracing and the clearances required may be to constrictive to allow for a rigid frame.
 
Side Note: Now as far as cable bracing.  True cables tend to stretch farther than rods and need more maintenance attention to keep them snug.  Rods are better than cables in my opinion.  Other options for sidewall bracing could include single angle bracing , double angle bracing, chevron bracing, k-bracing, portal frames, 1-legged portal frames, portal braces, fixed base posts/columns, diaphragm action of walls, or any other structurally sufficient bracing scheme (similar to conventional buildings... same options)

HTH,
Greg Effland, P.E.
KC, MO USA

-----Original Message-----
From: Mark Baker [mailto:shake4bake(--nospam--at)earthlink.net]
Sent: Tuesday, March 12, 2002 11:51 AM
To: seaint(--nospam--at)seaint.org
Subject: metal bld'g. cable cross bracing

We are presently doing foundation design for some metal buildings. We are not responsible for review of manufacturers drawings but I am scratching my head about something.
 
Is there something unique to manufactured metal buildings that allows them to use both vertical (in wall) and horizontal (in roof) cable cross bracing for lateral resistance?