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RE: WOOD - Engineered Lumber vs. Sawn Lumber

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In answer to your second question, I believe the odd widths (e.g.
5-1/8") are because the glulam needs to be planed on the vertical edges
after lamination.  (Have you ever been in a lam plant and seen what a
beam looks like after it comes out of the press?  Glue slops all over
the wide faces from between the lams, not a pretty sight.)  Come the
revolution and we all go hard metric, maybe mfr'd sizes will make more
sense.  My wife (and framing partner) still can't get over the fact that
a 2x4 doesn't measure 2" thick!

> ----------
> From: 	Dennis S. Wish PE[SMTP:wish(--nospam--at)cyberg8t.com]
> Sent: 	Monday, September 08, 1997 4:16 PM
> To: 	seaoc(--nospam--at)seaoc.org
> Subject: 	Re: WOOD - Engineered Lumber vs. Sawn Lumber
> 
> 
> 
> -----Original Message-----
> From: Richard Lewis <rlewis(--nospam--at)techteam.org>
> To: seaoc(--nospam--at)seaoc.org <seaoc(--nospam--at)seaoc.org>
> Date: Monday, September 08, 1997 9:17 AM
> Subject: WOOD - Engineered Lumber vs. Sawn Lumber
> 
> 
> 
> >>Dennis, if you don't mind I would like to start a new topic from
> something
> >you stated in you previous email.  BTW, I'm behind you also, I think
> you
> >documented yourself well and had this been for a larger fee, would
> have
> been
> >able to justify it in court.
> >
> >Now, my question is, why would you not use engineered lumber for such
> a
> large
> >span, like a Microlam beam?  It is stronger, stiffer and straighter.
> Would
> >the cost have been much different?
> >
> >DF #1
> > Ix=697 in.^4
> > Sx=121 in.^3
> > E=1,600,000 psi
> > Fb=1,350 psi (I am not sure which of the many species of DF you use
> in the
> >NDS)
> > Fv=85 psi
> >
> > Max Moment = 13,613 ft.-lbs.
> >
> >            E * Ix = 1.1152E9
> >
> >Microlam 1-3/4 x 11-7/8
> > Ix=245 in^4
> > E=2,000,000 psi
> > Fb=2,925 psi (depending on the species available in your area)
> > Fv=285 psi
> >
> > Max Moment = 10,060 ft.-lbs per ply
> >
> > E * Ix = 4.9E8 per ply
> >
> >Therefore 2.3 plies (actually 3) of Microlam are needed to equal the
> >stiffness of DF#1, but if stiffness didn't control then Microlam
> blows DF#1
> >out of the water based on moment and shear.  Maybe 2 plies would have
> worked.
> > Would 2 plies of Microlam cost significantly more than a single 6X12
> beam?
> >Does most of the profession use sawn lumber or engineered lumber in
> these
> >conditions?
> >__________________________________________________
> >
> >Richard Lewis, P.E.
> >Missionary TECH Team
> >rlewis(--nospam--at)techteam.org
> >
> 
> No question about it - an I am licensed to TJ for their TJ-Beam
> program. I
> guess at the time I found that a 6x10 worked with, what I considered
> to be
> acceptable deflection limits for this span. The other decision was
> that the
> wall was actually a double 2x6 wall constructed to satisfy and
> architectural
> detail and to provide the thick Adobe look.
> In retrospect,  a Parrallam is much more desireable, but it was a
> decision
> made at the time and I felt that the calculated deflections were
> acceptable.
> The measured calculations reflect a problem that I feel was proven to
> be due
> to a "crowning" of the delivered member.
> 
> While we are on the subject - Why is it that Trus Joist (or Lousiana
> Pacific
> or the other manufactered wood products companies) do not provide
> manufactured beams in conventional depths to sawn lumber. Why not
> produce a
> 5 1/2" x 11 1/2" member rather than an 11 7/8" beam. I have had to
> juggle
> details in order to fit a manufactured beam into locations where I
> could use
> a sawn lumber.
> Why, too, are Glu-Lam beams not made in conventional widths - ie, 3.5,
> 5.5.
> It would be a lot easier to get a beam in a wall that was 5 1/2"
> rather than
> 5.125?
> It would be understandable if the posts and studs supported these
> widths or
> depths, but I think it makes detailing more difficult.
> 
> Here we go again?
> Dennis Wish PE
> 
> 
> 
> 
> 
>