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Re: R value for log walls

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At 02:31 PM 12/8/99 -0500, you wrote:
>I am in the process of developing a MathCAD template for 
>determining seismic loads per UBC.
>However, I need to determine a realistic "R" value to assign to log 
>walls acting as both shear and load bearing walls. Obviously, a wall 
>constructed of logs stacked 1 above the other has a higher density 
>than a light framed shear panel, but is not as dense as a concrete 
>or masonry log wall.
>Does anyone have any suggestion, is there a calculation method to 
>determine it based on the material density???
>Any help will be appreciated
>Peter McCormack
Peter, a great opportunity knocks for you.

Other replies, especially by "sasquake", call attention to the committee
process as the source of seismic R values for various forms of construction.
It appears that no committee has yet undertaken to set an "R" for log
houses. In my experience on such committees, and following things since
then, a special coefficient for such an esoteric form of construction would
be tasked to one single person. If that person came back with a lot of
numbers on paper, etc., and presented the recommended outcome in a
self-assured, authoritative manner, then acceptance by the rest of the
committee with little hassle is very likely. Once that happens, the outside
reviews and cementing of the R factor outcome with the vaunted "consensus
process" proceeds apace. Ben Yousefi told us how that consensus position
becomes impenetrable armor against later challenge, especially one from an

So, you aren't on the committee, let alone a long-term member of it? For
shame! But all is not lost: Imagine you are a committee member, using
affirmation techniques and whatever else it takes to become a believer.
Behold: The committee has given you the job of developing the "proper"
R-value for log houses. Do it. Read up on the SEAOC Blue Book Commentary,
and maybe ATC and NEHRP commentaries to get a flavor of the rationale and to
pick up ease with the jargon. Then make up your mind firmly and set forth
your R value with resolve. That's how to do it. 

You don't have to furnish any scholarly explanation, or even any simple one,
because someone else writes up all that for the next edition of Commentary
later. Just be forceful in presenting it orally in committee, in your mind.
Then use this R value. 

Now, watch out for any second thoughts. You absolutely have to wrap yourself
in the mystique of committee membership, in your mind, even though you are
an individual. This is the magic that distinguishes you from any other
individual, such as the hapless one who submits a challenge during that
eleventh hour step in the final code approval process.

Good Luck, and Unshakeable Resolve. When you're done, tell us what R value
we have to follow. Logs "R" Us.

Charles O. Greenlaw, SE  Sacramento CA