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Re: Wood Fr-Upgr : What I'll do and two more questions

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Dennis S. Wish PE wrote:

> One last question. Inasmuch as there is insufficient exterior shear in the
> walls, do I shear the common walls of the new/existing construction for the
> the difference in shear caused by the new addition, or do I go back and try
> to determine the shear from the old section also acting in this wall and
> combine them?

Dennis:

If you are adding load to an existing wall then that wall must meet current code
(See UBC 3403.3, second paragraph) other wise you have an unsafe condition.
With regard to combining the existing and new loads, you might want to try an
"ABK" like approach for the existing loads such that the demand is not the
calculated tributary load but rather the capacity of the existing diaphragm to
deliver that load.  The new load from the addition should be full code and the
shear wall(s) should meet current capacity and aspect ratio requirements.  Good
luck.

Bob Bossi