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Re: GL beam strengthening
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 Subject: Re: GL beam strengthening
 From: "Dave Gaines" <gainesengr(nospamat)earthlink.net>
 Date: Fri, 2 Jun 2006 15:59:37 0700
Joe,
The 16 1/2 inch beam takes a larger portion of the
load, based on a percentage of EI for both beams, or a proportion of h^3 if
b and E are equal. You need to transfer that portion of shear
that the 16 1/2" takes back into the 12" GLB with bolts or hangers. You
need the bolts to take all of the shear very near the ends or transfer it
continuously back into the 12" beam. How about placing the 2nd beam
underneath the first beam with a saddle hanger over the top beam, much like a
beam hinge hanger? Use a saddle over the top beam with a field welded or
bolted steel connection to the bearing plate under the larger bottom beam.
You might have to remove one sheet of plywood above each end to insert the
saddle. The combined beam would be 28 1/2 inches deep.
If the new saddle hanger fix is hung close enough
to the end, the shear problem in the smaller beam may go away because the
distance from the new hanger to the bearing point may be less than the d
distance of the smaller beam. Don't dap the top beam for the saddle
or you'll reduce the thickness.
You can't add the second beam and expect it to take
it's share of the dead load unless you shore the beam that is in place, which
is taking dead loads already. You have to take the loads off of the
first beam before adding the second beam by shoring it up straight or to
the original camber.
If the first beam is 12" and second beam has
to be 16 1/2", what was the size of the beam that was intended for this
location? The combined I is 3499 in^4 and S is 468.3 in^3. Was the
originally designed beam a 6 3/4 x 19 1/2 or 6 3/4 x 21 ?
Steel channels bolted on both sides of the 12" beam
could also work.
I hope that helps.
Dave Gaines
Gaines Engineering
Pasadena, CA

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 GL beam strengthening
 From: Joe Grill
 GL beam strengthening
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