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RE: "Flitch-plate"

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"Standard" flitch plates run the full length of the beam.  When used as
a beam to support floor joists, the 2x wood members are typically on the
outside with the joists framing into them (using a ledger or joist
hangers).  The load is shared with the steel plate by transferring load
in shear with through bolts.  At the ends the plate as well as the wood
typically bears on the same support but sufficient bolts are usually
furnished to transfer most the load back into the wood (since it has a
larger bearing area).  Architectural Graphic Standards, 9th edition (and
probably earlier editions as well), has an illustration on page 295,
Lintels for Wide Openings (Rough Carpentry - Framing Details for

Ed Marshall, PE

> -----Original Message-----
> From:	Bill Allen, S.E. [SMTP:billallen(--nospam--at)]
> Sent:	Thursday, May 14, 1998 7:49 PM
> To:	seaoc(--nospam--at)
> Subject:	RE: Need "Flitch-plate" design example
> 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?
> Regards,
> Bill Allen
> -----Original Message-----
> From: Roger Turk [mailto:73527.1356(--nospam--at)]
> Sent: Thursday, May 14, 1998 4:41 PM
> To: seaoc(--nospam--at)
> Subject: RE: Need "Flitch-plate" design example
> I have used steel plates to reinforce wood beams, but never with the
> steel
> on
> just one side.  The way I looked at it was if you could use steel side
> plate bolted connections on wood members you should be able to bolt
> steel
> side plates to a beam to reinforce it.  The criteria is that the steel
> side
> plates must deflect vertically the same amount as the wood beam and
> then
> install enough bolts so that that portion of the load is distributed
> to the
> steel plates.  Because steel is so much stiffer than wood, steel
> usually
> ends
> up taking about 90% of the load.
> For spacing of the bolts along the compression edge of the steel
> plate, I
> use
> AISC's maximum spacing of bolts for a cover plate on a built up member
> (Sect.
> E4).
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona