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Re: Completly shearing a building (also answertoperforatedshearwalls)

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Chuck-
Our office also usually completely sheaths all
exterior walls with plywood.  However, plywood is
NOT a waterproofing element.  I don't know who told
you this, but it certainly is not true.

Ignoring the "narrow bits" based on the assumption
that they are "soft and/or weak" is also certainly
not necessarily true.  The stiffness of the pier is
related to the height to width, not just the width. 
These piers usually do not have holdown slippage
associated with them as a "full" pier will.  There
usually are full height king studs on either side of
the narrow pier.  

A pier that is only two foot wide and is also two
feet high, and has full height king studs either
side of the opening can have a significant effect on
the overall stiffness of the wall line.  

Lynn



chuckuc wrote:
> 
> Dennis-
>     In No. Cal., most engineered wood framed buildings are completely sheathed.
> The sheathing serves a critical waterproofing function, particularly under board
> sheathing.  In wet, windy conditions the omission of the sheathing is a very
> risky proposition.
>     The structural contribution of  these narrow bits and pieces is also
> ignored.  They tend to be soft and/or weak and probably have a similar effect as
> GWB.  They contribute to early stiffness but after a few major load cycles they
> get too soft to contribute significant strength or stiffness.  However, they
> probably absorb a fair amount of energy and provide significant damping.  Keep in
> mind that we, in effect, divide the load by an arbitrarily chosen R factor in an
> attempt to account for a multitude of dynamic effects and redundancies.
>     I don't know where you got the idea that the new code encourages engineers to
> try to fine tune a wood sheathed LFRS.  The commentary should make it clear that
> this is neither possible, practical, or even desirable.  It is hard enough to get
> proper construction of one or two types of shearwalls in a building.  To specify
> a fruit salad assortment is an invitation to construction screw-ups.  To get
> upset when the framers add sheathing or nails is also foolishness-- the analysis
> isn't that accurate to begin with!
>     I again recommend that you read the latest publication from CUREe
> (particularly Ed Diekmann's paper "When 2+2=0").
>     I also think Chrisopher Wright is correct.  The most important thing we can
> do is to provide/require thorough structural inspections by licensed engineers.
> There is probably nothing wrong with Conventional framing as long as it done
> correctly.  I've seen plenty of engineered construction that scared the heck out
> me--even after it was  "inspected" and approved by the EOR.  KISS and Inspect is
> my motto these days.
>     Chuck Utzman P.E.