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Re: Reinforcing Existing Beam

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This is one of those problems where the composite beam size is much
larger than you would get if you just put a new beam in.

Here are a couple of other ideas that you might consider:

1. Try a beam below the existing one that is only connected say at the
mid-span to the existing beam (non-composite). Since this is an
indeterminent problem, you will have to  model it and take into account
the relative stiffnesses of each beam. Adjust the size of the lower beam
until you can adequately control the stresses of each beam. You might
consider adding an additional shim plate between the beams that is
thicker than the space between them, thus preloading each beam. This
should unload the upper beam and load the lower beam according to their

2. You may also want to consider creating a king or queen post truss out
of the existing beam. You may do this either below the existing beam or
within the depth of the beam web. Adjust your dimensions and rod size
until you converge on a solution. Check your additional axial force and
shear in the original beam. You may also want to consider preloading.

Jim Kestner, P.E.
Green Bay, Wi.