Contractor-fabricated GL Arch
Contractor-fabricated GL Arch
(OP)
Have a proposed job to look at involving a built-up wood arch spanning 48 feet with a 24 foot high ridge, spaced at 12' centers forming a kind of quonset structure.
The contractor/owner wants to fabricate it on site using DF#2 material with special jigs, glues, bolts, and construction equipment. Considering the low stress grade of DF#2 for 1" members, has anyone found any allowance in the codes/standards, other than testing, to increase the bending stress above the standard 1000 to 1200 psi range, into the range of a laminated GL beam - 1600 to 2400 psi? I highly suspect not without special testing, inspection, and certification, but I thought I'd ask anyway.
The contractor/owner wants to fabricate it on site using DF#2 material with special jigs, glues, bolts, and construction equipment. Considering the low stress grade of DF#2 for 1" members, has anyone found any allowance in the codes/standards, other than testing, to increase the bending stress above the standard 1000 to 1200 psi range, into the range of a laminated GL beam - 1600 to 2400 psi? I highly suspect not without special testing, inspection, and certification, but I thought I'd ask anyway.
Mike McCann
MMC Engineering






RE: Contractor-fabricated GL Arch
I believe that the only stress grades that go above Fb=1500 psi is Machine Stress Rated (MSR) Lumber. The design values are found in Mechanically Graded Dimension Lumber (Table 4C in the 2001 NDS Supplement). But, I don't know if they run MSR for 1x wood.
You might give the APA in Tacoma a call at (253) 620-7400
RE: Contractor-fabricated GL Arch
Mike McCann
MMC Engineering
RE: Contractor-fabricated GL Arch
RE: Contractor-fabricated GL Arch
RE: Contractor-fabricated GL Arch
For 40' arches spaced 12' o.c. I am surprised that anyone would try to field fabricate the arches. Glulam plants are set up to do this sort of thing on a daily basis. It would be hard to imagen that the contractor could same money by gluing up the arches in the field. Particularly now with our slow economy, plants should be hungry for work.