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RE: High shear diaphragm value

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There are two topics in this thread.  We have different recommendations on “high load diaphragms” and “high load shear walls”.  For high load diaphragms, ER-1952 and the IBC cover the topic well.  Also see APA Research Report 138 for data supporting our recommendations.


For double sided shear walls (or perhaps “high load shear walls”), we have indeed conducted some testing as shown in APA Research Report 154.




Thomas D. Skaggs, Ph.D., P.E.
Senior Engineer
APA - The Engineered Wood Association
7011 S. 19th Street
Tacoma, WA 98466
ph: 253/565-6600
fx: 253/620-7235



From: Donald Bruckman [mailto:bruckmandesign(--nospam--at)]
Sent: Thursday, February 01, 2007 09:30
To: seaint(--nospam--at)
Subject: RE: High shear diaphragm value


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?




From: Marlou B. Rodriguez, S.E. [mailto:mbrodrig(--nospam--at)]
Sent: Tuesday, January 30, 2007 11:13 PM
To: seaint(--nospam--at)
Subject: RE: High shear diaphragm value


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

From: DA ENGINEERING [mailto:dnae(--nospam--at)]
Sent: Tuesday, January 30, 2007 2:12 PM
To: seaint(--nospam--at)
Subject: High shear diaphragm value



I'm looking for high shear diphragm value




Thanks in advance

Dave A., P.E.