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Strengthening Existing glulam

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Simon, Michel (& List):
It is true that moisture fluctuation affects the strength of the wood;
however, the additional contribution from FRP will not be influenced by
the moisture content of the wood -- provided that the epoxy being used
can tolerate the moisture and is tough enough.  I have provided a link
below to the article that was published in the Feb 2004 issue of
Structure Magazine:

http://quakewrap.com/news/Structure%20Magazine.pdf

As you see in Fig. 3, the strengthened beam has significant ductility;
in fact, at the end of the test, when we managed to pry away the carbon
fabrics from the face of the beam, we noticed that the beam section
around the midspan had completely failed in compression and tension. 
So, we had a "flexural hinge" there but yet, the ability of the beam to
maintain its load carrying capacity (as shown in Fig. 3) is amazing.

I am not sure if there are any provisions in the codes that require a
wooden beam to remain visible.  As to termites, the presence of FRP
will make it very difficult for these creatures to get into the beam. 
Even if they did, the ductile failure mode of the beam provides some
degree of assurance against catastrophic failure.

I hope this has been helpful.

Mo Ehsani, Ph.D., S.E.
Professor of Civil Engineering, Univ. of Arizona and
President, QuakeWrap, Inc.


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