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Re: High shear diaphragm value[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: High shear diaphragm value
- From: "Robert Kazanjy" <rkazanjy(--nospam--at)gmail.com>
- Date: Thu, 1 Feb 2007 11:00:47 -0800
.....Has anyone read any specific testing of the various failure modes of a high nailed, (2 or 3 inch OC), two sided, high load, site built shear walls and any specific differences that might imply an added safety factor should be considered? ........
Yeah, I hear you on that "sniff test" when I first was exposed to that concept I was skeptical as well.
On the few tests of doubled sided (4x8) shear wall that I did & can remember the results sill crushing under the end posts was a big factor. Again without digging out 7+ year old data, my recollection that double the capacity wasn't too bad an estimate. The HD's had to be very burly though, bumped up the bigger ones than the numbers would indicate...none of that using a Simpson HD indicated by the nominal design values.
Of course, this was a while ago before SImpson started to provide some deflection @ load info.
The allowable cross gain compression numbers are optimistic IMO. The compression strength of treated sill material is even lower, I've seen treated sill have the liquid squeezed right out of them.
Shearmax pref-fab panels stop their sills short of the post so you get those good end grain bearing strengths.
4x6 post are a good idea for double sided shearwalls....you can use them in 4" walls as well.
UBC never addressed it and I spent a lot of time combing APA reports on shear walls and I've not seen much, if any, data on any differences between single and double sided shear walls. As far as I've seen, APA merely seems to extrapolate that a 2 sided SW is exactly twice as good as single sided. That just don't pass the smell test for me.
I've had carpenters add nails into two sided shear wall framing until, to our view in the field, there seemed like there had to be some effect on the wood as a result of so many nails. Anecdotally, the carpenters tell me, "you can run any numbers you like, but I'm telling you that with today's lumber quality, the 4x4 ends are compromised with all those nails." Now, I'm not one to pay much attention to field comments like that, but in some respects, those are the guys that know the wood the best, so, while telling them, "…shut up and build it…", I've quietly made it a habit to always make double sided shear walls a 2x6 wall, giving me 4x6 ends to nail to.
Has anyone read any specific testing of the various failure modes of a high nailed, (2 or 3 inch OC), two sided, high load, site built shear walls and any specific differences that might imply an added safety factor should be considered?
Look at ER-1952. This uses multiple rows of 14 ga staples or 10D nails to achieve high allowable values for diaphragms.
Marlou Rodriguez, S.E.
MBRodriguez Engineering Inc.
2355 Oakland Road, Suite 14
San Jose , CA 95131
Tel: (408) 432-4866
I'm looking for high shear diphragm value
Thanks in advance
Dave A., P.E.
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