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Re: Shear Walls and 3x Framing (UBC) STAGGERING

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Tom
While I don't think there is anything wrong with the nail placement David has cited, I've drawn the detail on my drawing the way that best emphacizes the stagger I really care about (to avoid same grain splitting).

Now that we've settled that, lets talk about dimensions.

1. 2x framing with 6" spacing & 2 rows of nails: If you use 3/8" edge distances there's no way to create a 1/8" gap between sheets (unless the outer row is driven at an angle). The carpenters normally omit the gap.

2. With 3x framing & 4 rows of nails: IIRC correctly 1/2" edge distance is prefered (I ran some simple lap shear tests & found about a 15% strength increase over 3/8"). So with .5" at the edge & .5" between rows, the edge distance on the stud is only .25" (again omitting the gap). The best solution is 4x at the panel edge.

On a somewhat related subject, what are people doing about the very tight spacing that you get with steel strapping? The last time I asked Simpson (maybe 3 years ago) they told me the strap allowables were calculated, not test results. I usually double the strap length & nail every other hole. Placing a long row of 16 sinkers at 3" or 4" o.c. seems like a really bad idea.

Comments?

Chuck Utzman, P.E.

Tom Skaggs wrote:

Mr. Merrick:

Although I agree that the below mentioned publication has the graphic as
shown, I think this was "artistic license" instead of intent.  IN fact,
it is my recollection that our helpdesk has drawn a figure that is more
similar to Chuck Utzman's below graphic.

From our perspective, the intent of staggering is to reduce the
potential for splitting.  The illustration in L350G is intended to show
the staggering parallel to the framing.  The staggered perpendicular to
framing is simply coincidental.

Tom

-----------------------------------------------------------------------
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
-----------------------------------------------------------------------



-----Original Message-----
From: David Merrick [mailto:mrkgp(--nospam--at)winfirst.com] Sent: Tuesday, December 16, 2003 10:25
To: SEAINT
Subject: Shear Walls and 3x Framing (UBC) STAGGERING

I have The "Diaphragms and Shear Walls Design/Construction Guide"  2001
APA (APAL350G.PDF). Page 32 shows that the staggering of nails is to be
in both directions, parallel and perpendicular to the stud. I took Mr.
Utzman's graphics and corrected it. The above reference is the only
reference I have ever found that clarifies the problem. What would we do
with out APA?

Here is what page 32 shows...

      o            o          o          o
o            o         o            o
_____________________________
      o            o         o            o
o            o         o            o


I got the first conclusion from purely the code, by observing how the
terms "stagger" and "offset" are used and related them to a possible
directional relation with the stud. I also applied the engineer's
comment that it is "impossible to staggered".  That is true if
staggering at joining edges means to have four rows of nailing and a 2x
is allowed. The table 23-II-I-, note 4 states  "Plywood joint...nailing
shall be staggered in all cases"
That, as a separate sentence, might be interpreted to include a "case"
of shear less than 350 lb/ft, where a 2x is allowed. If that is used,
then staggering is impossible if meaning "four rows of nailing".

I recommend designing with the APA guide, but question condemning some
varying staggerings. When should nailing be pulled and renailed? When is
a stud over nailed and needs replacing?

David Merrick, SE


From: chuckuc
Subject: Re: Shear Walls and 3x Framing (UBC)

David-

Hmm--where did you get that idea that staggered nails are in a single
line? "Offset" panels are arranged so as to keep splitting loads from
highly loaded edges from falling on the same stud (requiring a panel
displacement of 16"). Staggering nailing is intended to avoid stud
splitting (ideally .5" to avoid same grain splitting problems).

Like this:

      o            o          o
o            o         o            o
_____________________________
o            o         o            o
      o         o            o



Not  like this
o         o          o        o            o
_______________________________
   o          o          o            o


I finally added a little detail on my drawings to clarify.

Chuck Utzman,P.E.


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