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Re: Reinforcing Wooden Beams

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<I am looking for a good reference that covers the subject of how to
reinforce existing wooden beams with steel plates. I'll appreciate any
help.>

I don't have any references but if I were doing it I would:

1.    Use modular ratio to convert wood to steel (multiply width of beam by
Ewood/Esteel).
2.    Calculate section properties I and Qs at centroid of the composite
section and at the steel to wood interface for composite section using area
of steel and converted area of wood.
3.    Check flexural stresses in steel and wood of composite section (My/I)
considering compression buckling in steel plate (i.e. how often would it
have to be connected to the wood to prevent buckling). Stress in  wood be
Ewood/Esteel times the calculated stress in the appropriate point in the
composite section.
4.    Check shear stresses in composite section (shear flow is
VQcentroid/Icomp) If steel is reinforcing the flanges only this might result
in high shear stress in the web of the wood beam. You might consider
reducing the shear stress calculated using shear flow by a factor of 2/3
since allowable shear stress in a wood beam is calculated using V/bd but
peak shear stress at mid depth of a rectangular beam is actually 1.5 x V/bd.
5.    Calculate shear flow between steel and wood and design connectors
accordingly (probably shear plate connectors if the wood beam is heavy
timber).
6.    Check deflection of composite section using Esteel Icomposite.

Hope that is some use,
John MacLean



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