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RE: factory-made roof trusses

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{Roger Turk}
Since most pre-fab truss fabricators use computer analysis provided by the
plate manufacturer, which kicks out *anything* that is permitted by the

This reminds me of something I have been curious about on truss submittals.
In their computer output(Alpine) there is usually a little box labeled
something like allowed stress increase and in my area (Central Alabama) the
box is usually labeled 1.15.  The code does allow a repetitive stress
increase  of 15% for bending members provided you meet a few requirements.
This is not clearly spelled out the way the little box is described on the
output.  My interpretation of the output is that everything is bumped by 15%
therefore I always write in 1.00 and mark the shop drawings "Make
corrections noted"  Has anyone run into this before and do you know if the
program is, in fact, only bumping the Fb by 15%.

PS On our drawings and specs we always require that the shop drawings and
calcs be stamped by a licensed (registered ->whichever it is this week)
engineer in the state that the project is taking place in.  We also do this
for Light Gauge steel trusses.


John Jones, EIT
Pell City, AL