Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Need "Flitch-plate" design example

[Subject Prev][Subject Next][Thread Prev][Thread Next]
That's the way we've always done it as well.  This pattern can even be
repeated to create wider (sitffer) beams.  The assumption we've made,
and it has always worked is that the plate carries all load and that the
wood "braces" the plate from torsional buckling.  I usually don't use
full (0.66Fy) plate bending stress, however, just to help with the "warm
fuzzy" idea.  Bolts are placed to transfer a rational amount of this
"bracing" force to the lumber (2% per Yura?)  We have not restricted
ourselves to 1/4" plate however. (Although contractors on the typical
"flitch beam" size job tell us that 1/4" plate or 3x3 angle iron will
hold up anything) We will let deflection find the depth (in lumber
increments, or depth available obviously), and let Sx at 12-15 ksi find
the plate thickness.  HAs our rationale any logic or should we be losing
some sleep tonite?

>-----Original Message-----
>From:	Ed Marshall [SMTP:elmarshall(--nospam--at)]
>Sent:	Thursday, May 14, 1998 5:46 PM
>To:	'seaoc(--nospam--at)'
>Subject:	RE: Need "Flitch-plate" design example
>Sounds like we may be thinking of different things.  The flitch plate
>beams I'm thinking of are assemblies with a vertical steel plate
>sandwiched between doubled-up joists.  It is not a composite design in
>that there is no horizontal shear transfer.   The typical application is
>a location where beam depth is restricted.  A pair of 2x10's with a
>1/4"x 9 1/4" plate assembled together makes a 3.25' wide beam, but has
>roughly the stiffness of an 8x10 timber.  
>Ed Marshall
>> -----Original Message-----
>> From:	Bill Allen, S.E. [SMTP:billallen(--nospam--at)]
>> Sent:	Thursday, May 14, 1998 6:07 PM
>> To:	seaoc(--nospam--at)
>> Subject:	RE: Need "Flitch-plate" design example
>> I guess where I am "extrapolating" information is with regards to GLB
>> strengthening. Years ago, I occasionally reinforced overstressed GLBs
>> using
>> this method. I then ran into a GLB expert (one who has 40+ years
>> experience
>> and now spends a lot of time in court as an expert witness) who said
>> this is
>> a bad idea and will not perform over the long haul.
>> With regards to residential construction, collar ties seem to perform
>> well
>> too, but they won't "calc out" based on some of the modeling I have
>> done
>> (due to horizontal deflection).
>> My previous post was my $0.02 and was merely cautionary. My friend
>> Dennis
>> Wish can do whatever he desires.
>> Regards,
>> Bill Allen