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Re: Pitched Tapered Glu-Lam

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Indeed the 15 psi is a low value for radial tension (tension perpendicular to
grain) for Western Species (includes Douglas Fir -Larch, Hemfir, etc.) glulam.

However, I disagree with the statement that it is a catastrophic failure.
Double pitched and tapered (DPT) glulam beams will sag, but I have yet to hear
of a beam that has fallen to the floor/ground. I investigated one situation
where the DPT beams sagged two feet under a snow load of 60 or more psf that
were designed for 30 psf. One of the beams even fractured to the extent that
the bottom tension lamination was broken, but it did not fall. If you know of
a failure, I would appreciate hearing from you.

 AITC now has a recommendation for designing DPT glulam beams for Western
species. It shows how to design reinforcement (steel rod or rebar in epoxy)
to prevent the "smile" that can occur due to the radial tension. Southern Pine
has a much better value for radial tension and many of those designs do not
require reinforcement.

Contact AITC at 303-792-9559 for more information.

Bruce Pooley, P. E.