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Re: wood adhesives / GLB cracks

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Tom Harris

For pedestrian bridges, the glulam beams are typically specified to be
pressure preservatively treated. The "cracks" in the glulam beams are probably
seasoning checks, which may have been "enhanced" by the treating process. The
fact that the beams look dirty is also an indication that the beams were
probably treated. 

The American Institute of Timber Construction (AITC) has a technical note to
evaluate the effect of checks on the capacity of glulam beams. I am not aware
of any sections in the building codes that limit seasoning checks. You may
wish to contact Mike Caldwell at AITC, 303-792-9559.

Having worked for AITC for nearly 10 years and having conducted many field
investigations, checking of the beams is typically not a structural problem.
What needs to be done is have the beams inspected by a "qualified" engineer or
wood technologist to verify that the cracks are indeed seasoning checks or
delamination of the glueline. May I suggest that you contact the glulam
manufacturer. In many cases, they, or an independent inspector, will inspect
the beams to verify compliance with standards and job specifications.

If you need further assistance, please contact me.

Bruce Pooley, PE
Timber Design
3448 South Newland Court
Lakewood, CO 80227 
phone 303-989-8701 (evenings) or 303-235-2768 (daytime)