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Re: Completly shearing a building (also answertoperforatedshearwalls)

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UBC Section 2506.4 requires minimum two layers of Grade D paper for wood
sheathing  when stucco is applied. This would be indicative of the lack of
weather protection of the wood sheathing.


----- Original Message -----
From: Lynn H <lhoward(--nospam--at)silcom.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, September 20, 1999 6:58 AM
Subject: Re: Completly shearing a building (also
answertoperforatedshearwalls)


> 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.
>
>