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RE: Need "Flitch-plate" design example

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Bill,

I think that you may have misunderstood my post.  The design of the plates 
was not extrapolated from cover plate requirements.  I recognized that the 
compression edges of the plates are subject to buckling and maximum 
longitudinal spacing of bolts is necessary to prevent the buckling.  Cover 
plates of steel members subject to compression are also subject to buckling 
between bolts, and there is a longitudinal spacing limit on fasteners for 
this condition.  I considered this a conservative requirement for a plate 
subject to bending and applied that limitation to bolt spacing along the 
compression edge of the plate.

I will send you a FBD sketch for your comments.


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

Bill Allen wrote:

. > It would be interesting to see a free body diagram which shows how the 
. > load goes from the wood member to the steel plates and then, at the ends 
. > of the steel plates, from the steel plates back into the wood member. If 
. > the steel plates are supported by the same structural element as the 
. > original wood beam and the two (wood beam and steel plates) are fastened 
. > together, it would make sense that the load would be distributed 
. > proportional to the relative stiffness of the members. If the load is 
. > actually applied to the wood member, then the connection between the steel
. > plates and wood member can be determined by the equivalent load required 
. > to force deflection compatibility.
. > 
. > I can see how easy it is to extrapolate a design methodology from a cover
. > plate design for example to a problem such as this, but I do not thing 
. > this extrapolation is proper. Obviously, based on my responses, I am 
. > hesitant to use this repair method based purely on "home brew" 
. > calculations without some sort of computer modeling and long term testing
. > (including creep of the wood).
. > 
. > In my opinion, this repair method saves a modicum amount of construction
. > costs and may very likely invite the engineer of record into a courtroom.
. >