Three Hinged Glulam Arch - Wood Rot
Three Hinged Glulam Arch - Wood Rot
(OP)
I'm investigating a building consisting of 18 120' glulam arches spaced at 20' o/c. Unfortunately, the last six feet of the arches protrude through the building envelope and have, over the last 40 years, rotted significantly.
My question is this: will it be absolutely necessary to remove the rotted wood? I suspect so but want to be sure as the need to remove the rotten wood will complicate things considerably.
Is there any way that the rotten wood could be treated so as to neutralize it and keep the fungi from colonizing the competent wood beyond the rot? If I could somehow guarantee a low moisture environment (<= 19%), would that obfuscate the need to remove the rotten wood?
Thanks for your help.
My question is this: will it be absolutely necessary to remove the rotted wood? I suspect so but want to be sure as the need to remove the rotten wood will complicate things considerably.
Is there any way that the rotten wood could be treated so as to neutralize it and keep the fungi from colonizing the competent wood beyond the rot? If I could somehow guarantee a low moisture environment (<= 19%), would that obfuscate the need to remove the rotten wood?
Thanks for your help.






RE: Three Hinged Glulam Arch - Wood Rot
RE: Three Hinged Glulam Arch - Wood Rot
Mike McCann
MMC Engineering
RE: Three Hinged Glulam Arch - Wood Rot
That is an interesting conclusion. Why should moment capacity not be a problem?
BA
RE: Three Hinged Glulam Arch - Wood Rot
I am assuming here that the reaction points and crown connection are pinned. Maybe this is otherwise OP?
Mike McCann
MMC Engineering
RE: Three Hinged Glulam Arch - Wood Rot
BA
RE: Three Hinged Glulam Arch - Wood Rot
I did not mean to imply that the arch saw no moment between the hinges, but that the moment went to zero at the hinges. I'm sorry if my statement was not clear. The arch has a rather large span - 120 feet as stated by the OP. The maximum moments will be in the vicinity of the 30 and 90 foot points of the arch depending on the loading conditions. At the start of the rot, the moment should be 10% or less of the maximum.
All this structure is is two simple beams linked at a crown by a pin. Nothing more. The simplest arch.
Mike McCann
MMC Engineering
RE: Three Hinged Glulam Arch - Wood Rot
BA
RE: Three Hinged Glulam Arch - Wood Rot
RE: Three Hinged Glulam Arch - Wood Rot
RE: Three Hinged Glulam Arch - Wood Rot
Then for the repairs, they shored, then they cut section of the laminates and glued them back using gorilla glue (check the shear stress). They also have finger splicing between lams. For higher stressed areas (moment areas) they used some steel plates.
You should look into AITC documents.
http://www.aitc-glulam.org/
Some other repairs
http://www.spsconstruction.com/glulam.html
Also, Call AWC http://www.awc.org/index.html. I remember one of the directors performing an exact same repair. In this case they actually cut the end of the member, placed a new "bucket" steel bracket and pin and then provide a gap so water wouldn't acummulate at the end (sourec of issue ----don't let it happen again). I beleive they also installed anti-mold rods in the end. There may be a diagram in the AWC standards.