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# Re: More questions about rigid plywood Diaphragms

• To: seaint(--nospam--at)seaint.org
• Subject: Re: More questions about rigid plywood Diaphragms
• From: Seaintonln(--nospam--at)aol.com
• Date: Thu, 1 Jul 1999 18:19:42 EDT

```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
models.

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

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

```