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RE: WOOD: Visually Graded Lumber - "Ripping"

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Chuck,
I don't think I suggested designing one grade higher makes ripping
acceptable. In fact, I invited a representative of the WWPA to my
classroom about two years ago and what he said was that each member is
graded upon the number and location of knots and other deficiencies in
the wood piece - which would require re-grading of the piece. This is,
as mentioned, due to the location of the know in an area where tension
may be increased should the board be shortened and the knot occur closer
to the center of a uniformly loaded joist or beam. 

I might have stated that if using lumber where the grade stamp had been
removed, the engineer should calculate the lumber supplied based on what
was specified on the structural drawings and then assume one grade
lower. Most of us are not capable of grading lumber and it is difficult
to hire and have a representative of the WWPA appear at the job site to
review the lumber that remains. For this reason, it is always important
for the framer to keep the grade stamp intact on the lumber.

Dennis

-----Original Message-----
From: chuckuc [mailto:chuckuc(--nospam--at)pacbell.net] 
Sent: Sunday, September 28, 2003 2:59 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: WOOD: Visually Graded Lumber - "Ripping"


IIRC allowable knot size is also related to the board size.  Dennis has 
previously suggested that simply designing one grade higher makes 
ripping acceptable, but I don't think that's correct (unless your 
specifying clear lumber).
Comments?
C. Utzman, P.E.

Roger Turk wrote:

>Bill,
>
>Basically, if you rip a piece lengthwise, you are repositioning the 
>knots
>with respect to the edges on the piece.  Knots which may have been
center 
>knots could now be edge or spike knots; loose knots permitted in the
center 
>could now be prohibited loose knots at the edges.  ASTM D245 describes
where 
>in the piece knot provisions change.
>
>PS20-2002(? My copy of PS20 is in the office and I'm not) basically 
>says very
>little about detailed grading of lumber, but specifies the agencies 
>responsible for writing the grading rules for various species.  For
example, 
>WCLIB writes the grading rules only for Douglas Fir (Coast Region),
WWPA 
>writes grading rules for other western species, SPIB writes the grading
rules 
>for Southern Pine, etc.
>
>I doubt if AWS has anything to do with it (AWC maybe, but not AWS <G>).
>
>HTH
>
>A. Roger Turk, P.E.(Structural)
>Tucson, Arizona
>
>Bill Polhemus wrote:
>
>. > Someone mentioned here awhile back that if you take a dimension 
>lumber . > "board" such as a 2x8 and rip it lengthwise, the piece is no

>longer . > "graded" per the visual (or I presume, machine) grading 
>standards, since . > imperfections in the wood that go into the grading

>of it are not uniform . > across the section. You could have one piece 
>with a bunch of knots in it, . > for example, while the other is 
>relatively free of them.
>
>. > I am trying to find "chapter and verse" where this occurs in the
>. > literature. I assume it is a "PS" standard or similar put out by
AWS.
>
>. > Can anyone help me?
>
>. > William L. Polhemus, Jr. P.E.
>
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