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Re: Wood Moment Frame?

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The proposed wall has an aspect ratio of 5:1 and is not UBC compliant (see
Fig. 23-II-I b)--and that should be the end of the discussion.
It is certainly possible to build such a wall so as to meet the code
required drift limits, but it is extremely difficult if the loads are large
(and you'd need lab tests to prove it).  Simpson (and a few others) have
gone to great lengths to fabricate and test code compliant portal
frames--tell your guy to buy some.
The aspect ratio multiplies all the sources of deflection: construction
slop, shrinkage, tie down deflection, fastener deflection, plate crushing,
etc. 5:1 is a killer and the problem is not amenable to accurate calculation
even if you tried to control all the construction variables. (I don't even
think Simpson's tests with green headers are accurate because they didn't
allow their headers to shrink before they tested them.)
Chuck Utzman, P.E.


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