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RE: Need "Flitch-plate" design example

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Bill Allen wrote:

. > Sure, steel is stiffer than wood, but wouldn't the steel plates have to 
. > span to the reactions in order to get deflection compatibility? 
. > Otherwise, how does the load get into the steel plates?

Yes, Bill, the steel plates do have to be supported at their ends, but many 
things can constitute a "support."  The steel plates could be extended to the 
same element that is supporting the wood member, or, if the wood member has 
the shear capacity, the ends of the steel plates can be supported by bolting 
to the wood member, or, a steel saddle could be placed over the wood member.  
By connecting the steel plates to the wood member as near as possible to the 
end of the member, it is equivalent to having the steel plates supported by 
the same support as the wood member.

I have found it virtually impossible to get composite action with a wood 
member using mechanical fasteners, even with a wood-to-wood combination such 
as an inverted "T" and (for retrofit work) even if composite action is 
achieved, the neutral axis is shifted so much that the flexural stress in the 
top of the wood member exceeds the allowable.

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