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Fwd: Re: Notch Bottom of GLB

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Re:  Sasha Itsekson asked about notching the bottom of a GLB.

Absolutely NOT!!!

There are many more things to worry about than the bending stress. 
Remember, that when you notch the bottom of a GLB, you are subjecting
the laminations to *TENSION* perpendicular to the lamination.  This
will result in delamination/splitting of the GLB starting at the
re-entrant corner of the notch.  I investigated the failure of a GLB
that had a 2-inch by 2-foot notch put in it so that a flourescent
light fixture in a suspended ceiling would fit without lowering the
suspended ceiling.  (The contractor "repaired" the beam by putting
another GLB on the roof and running rods thru the roof to support the
framing on one side of the failed GLB.  Needless to say, the
contractor didn't do anything to protect the roof mounted GLB from the
weather, either.)

The only way that I would permit a notch in the bottom of any wood
beam would be to have mechanical connections (bolts) thru the beam
before and after the notch and some members to carry the force across
the notch.

A. Roger Turk, P.E.(S)
Tucson, Arizona 

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Date: 04 Apr 97 16:31:49 EST
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Subject: Re:  Notch Bottom of GLB
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Richard Lewis, P.E.
Missionary TECH Team

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