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Re: More questions about rigid plywood Diaphragms

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Our discussion some years ago had to do with the problems of calculating the 
actual forces on Rafter Tied Gabled roofs. The calculated forces for a rafter 
tied connection often does not work as the resulting forces require a much 
more sufficient connection that what is called for in the Nailing Schedule. 
The discussion concluded that the Rafter tied connection was probably 
determined emperically rather than by rational calculations.

Chuck Greenlaw convinced me that my perverbial butt is in jepordy if I don't 
abide by the code fabricated standard of practice (since it is not in keeping 
with the actual practices of the professional community during the reign of 
the '94 UBC) I'm in trouble. 
Nels has suggested that the analysis is pretty straight forward and other 
suggested that we really don't know what will happen until we create a few 

I know this may be a dumb questions, but hasn't the seismology committee 
modeled these system (gabled, scissor truss, vaulted roof systems) in the 
process of creating a deflection criteria?  If they had, why are the examples 
not provided for us to learn their "Intent".  It's great to be expected to 
comply with the intention of the code, but we have proved on this list that 
the intent never included light framed residential type structures. 

Has anyone on this list done the math for these types of structures and if 
so, how about sharing your results with us?

I'm no longer looking to debate, but am more concerned with understanding who 
to solve different models that are not rectangular or have various pitches.

Specifically, I would like to know how to solve a Donut Shaped Structre (with 
square sides and an Attrium in the Center, A "U" shaped structure and a "U" 
shaped structure where the diaphragms of the legs are 45 degrees to the 
horizontal rather than perpendicular, A two story where the lower story is 
cut into the hillside for sub-terranean parking (with masonry walls), and 
other types of unusual shaped structures.

Dennis Wish PE