While we are discussing roof trusses. Can someone tell me why the truss
manufacturers use the "Primary frames and systems" Wind Pressure Coefficients (Cq
in the '97 UBC Table 16-H), instead of the "Elements and Components"
coefficients. I don't see the justification. For wind uplift, the difference
can be significant, especially for the typical roof truss with less than a 100 sf
tributary area. I wouldn't design a roof rafter as a primary frame. What's the
difference with a truss?
If you think the trusses on your project are being designed as elements and
components, you might be surprised if you check the uplift reactions, I was.
Associated Design Consultants, Inc.