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Re: Wood Diaphragms

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nmoore(--nospam--at) wrote:

> 1.      Both the 1994 UBC and the 1997 UBC referring to sections 2314.1 and
> 2315.1 respectively state "DIAPHRAGMS, WOOD - Not acceptable as rigid
> diaphragm".

I have wondered about this as well.  1997 UBC 2315.1, second paragraph places no
mathematical limit on shear wall or diaphragm deflection only stability
consideration .  This provision has been in the UBC since 1955.

In 1988 the term "flexible" was first defined as being greater than 2x story drift.

My first question is:  Is story drift even limited in wood frame buildings?    I
would argue it is not (other than by stability limitations).  If it is, then 2315.1
conflicts with 1630.10.  Since, with respect to wood, 2315.1 is more specific
101.9.1 makes it govern over the general (all materials) provision of 1630.10.

If story drift is not limited by 1630.10.3. for wood buildings, then the definition
of flexible, which is based two times on the arbitrary limit would seem not to be

If I am correct then, I would argue further it is up to the design engineer's
judgment, not the code, to determine how to distribute diaphragm loads to shear
walls.  Andwasn't that the state of practice until recently?

I would like to see some feed back from others on this.  Perhaps John Rose?

Bob Bossi

So many codes, so little time!