From: "Bruce D Pooley" <bdpooley(--nospam--at)home.com>
Date: Wed, 30 Jun 1999 14:03:18 -0600
----- Original Message -----
Sent: Wednesday, June 30, 1999 12:36 PM
Subject: Re: Cutting a Glulam Beam
> In a message dated 6/30/99 6:20:30 AM Pacific Daylight Time,
> What a great way to learn. Thanks Barry, I had no idea. Does a GLB that
> not specified to be cambered arrive at the site with the top designated?
Bruce Pooley comment: Glulam beams are manufactured using either a balanced
layup or an unbalanced layup. For stock beams, balanced combinations (for
example, 24F-V8) are not required to have the TOP stamp. Unbalanced stock
beams, say 24F-V4, are required to have the TOP stamp.
There are generally to types of glulam beams -- custom or stock. Stock beam
are manufactured in "standard sizes" and shipped to lumber yards or other
distributors as "billets" that are most commonly 60 long. Both the quality
mark and the TOP stamp are required to be placed on the top of unbalanced
combinations at least every 8 feet.
> never really thought about this one and considered the plys to be
> all the way through.
Bruce Pooley comment: Most glulam combinations developed by AITC or APA use
several grades of lamination stock (2x lumber that has been milled with
specific moisture content limits, generally less than 16%, and thickness,
1.500 inches plus or minus 0.012 inches!
Laminating grades are shown in standard grading rules. For Douglas Fir -
Larch (species group), these grades are designated as L1, L2D (d is for
dense growth rate) , L2 and L3. AITC 117 Manufacturing details the amounts
and grades that are used in each glulam combination. For 24F-V4 Douglas
Fir - Larch, for a beam 30 inches deep (20 laminations at 1.5 inch thick)
the layup would be:
Top L2D designated as the outer compression zone
L2 designated as the inner compression
12 laminations of L3 designated as the core zone
L2 designated as the inner tension zone
L1 designated as the inner 5% of the outer
302-24 (replaces the L1) outer 5% tension
There are four grades of special tension laminations designated as 302-20,
302-22, 302-24, and 302-26. These special tension laminations are also shown
in the grading rules, except for 302-26. AITC 117 Manufacturing also
contains grading rules for these special grades.
> Therefore, Shafat, disregard my response except to recommend the client
> sectional door.
> << Yes.
> The tension lamination splices are specifically located in this zone and
> creep up into it's depth you may be getting into less desirable laps and
> Barry H. Welliver
> Draper, UT >>