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Re: Completly shearing a building (also answertoperforatedshearwalls)[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: Completly shearing a building (also answertoperforatedshearwalls)
- From: chuckuc <chuckuc(--nospam--at)dnai.com>
- Date: Sat, 18 Sep 1999 18:34:39 -0700
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.
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