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RE: Shear Walls and 3x Framing (UBC)

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Dave,
One point of clarification. I was using the term "over-nailing" to mean
penetrating the surface ply, crushing it or otherwise making the outer
ply useless. I did not intend my use of the term to mean adding nails
and hope this was not misunderstood.
Dennis S. Wish, PE

-----Original Message-----
From: David Merrick [mailto:mrkgp(--nospam--at)winfirst.com] 
Sent: Friday, December 12, 2003 2:02 PM
To: SEAINT
Subject: Re: Shear Walls and 3x Framing (UBC)

UBC table 23-II-I-1

Yesterday's discussion talked of staggering nails as being difficult or
impossible. The term stagger is to prevent nailing directly across from
each
other at abutting panels. That is not difficult or impossible. See note
2
where another term "offset" is used for the staggering delta that is
perpendicular to the stud. The term "stagger" is then for a delta
parallel
to the stud. The panel's edge nailing remains on one line.

Cool note by Thomas D. Skaggs, Ph.D., P.E. that the 350 pdf is  simply a
4
inch nail spacing.

Allowable capacity is not the design force, it is the capacity of the
actual
nailing. The term "allowable shear values" could be the "minimum
allowable
for capacity", but the term "Allowable Shear..." is the title of the
tabulated values for the specific nail spacing tabulated.

Over-nailing should increase the shear demand. The code might be
assuming
that 4 inch nailing of abutting panels will split a 2x, if the nails are
yielding with high deflections. Assumed ductility (or the ability to be
flexible) allows the code base shear be low. Over nailing could cause a
more
demanding rigid structure. If one were to use an allowable that is twice
the
demand (almost the omega factor) then I suspect over nailing and a rigid
structure is less of a problem. That could be why the 50% bolt-capacity
allowance is in note 3. Such an allowance in framing above, unlike the
assumed rigid sill bolting, may increase the demand, on the
whole-structure.

Carpenters, with the best of intent, are adding more nails. Does one
have
the extra nailing removed? When does too much nailing damage the stud?
(i.e.
10d @ 1.5"oc abutting panels over a 2x stud?)

David Merrick, SE


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