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glu-lams and termite damage

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Can anyone provide guidance in repair of an existing glu-lam beam with termite

In my particular case I have an existing glu-lam beam,  50 foot backspan with
a 11 foot cantilever that has termite damage at the midspan of the backspan.
The roof is a panelized system with 4x16 purlins at 8 foot on center by 24
feet long. The glu-lam beam is 5-1/8 x 30 and the initial visable termite
damage uncovered so far extends down at least 3 inches from the top of the
glu-lam.  The original design was tight, so by subtracting out 4.5 inches of
lumber for a net depth of 25.5 inches, the glu-lam no longer figures unless
the live load gets down to about 10 psf (dead load is 12 psf).  The length of
the visible damage along the surface is about 12 inches.  We plan on furthur
investigating the extent of damage, but before proceeding too far, I would
like to get the opinions or experiences of others.

The possible options that come to mind are:

1. Replace the glu-lam  (probably the most expensive)

2. Cut out the damaged part of the glu-lam and replace with new lumber (glue
and threaded dowels (assuming that the damage does not extend too deep into
the glu-lam).

3.  Add external reinforcement (king post with tension cable) to change member
to be primarily an axial loaded compression member (again assuming the damage
is not that extensive). 

4. Add column at this location (not the most desireable, but cheaper than
replacing the glu-lam).

There is other termite damage in the building requiring some of the purlins to
be replaced.  The building will be sprayed for termites and dryrot once all
repairs have been made.

Thanks in advance

Michael Cochran