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RE: Need "Flitch-plate" design example

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The comparison I was making to the cover plate design was that, in the cover
plate design, the cover plate need only extend about 12" beyond the points
where the unreinforced beam is overstressed. In this case, it is clear and
easy to see how the load is transferred into and out of the cover plates via
welding of the plate to the flange. I do not believe this analogy can
be/should be extrapolated to "flitch plate" designs because the load
transfer mechanism is different.

Bill Allen

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)]
Sent: Friday, May 15, 1998 11:52 AM
To: seaoc(--nospam--at)
Subject: RE: Need "Flitch-plate" design example


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
. > 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
. > 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
. > (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
. >