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]
I never thought this simple question would get so much play on the list.
Instead it yielded some very in-depth methodolgies. My original intent was
to plate the entire length of the beam. I never felt comfortable with
plating the tension side of a wood beam and the effects on the member due to
drying.
Thanks for the information. Due to time constraints (the contractor wants to
leave town by the weekend) we have decided to simply install a second 4x16
adjacent to the original and stitch them together.
I did receive advice from private email which helped me learn the design
process. I knew the basics but was unsure how to balance the deflection and
stiffness between two disimilar materials. I haven't done a composite beam
design for many years and admittedly am rusty on this.

However, I want to thank all of you who have responded. This type of peer
assistance is what makes the list so sucessful and so valuable to all of us.
I, for one, really appreciate all the help I have gotten since this list
started.

Thank you all again,
Dennis


-----Original Message-----
From: T [mailto:vicpeng(--nospam--at)vtcg.com]
Sent: Thursday, May 14, 1998 7:54 PM
To: seaoc(--nospam--at)seaoc.org
Subject: Re: Need "Flitch-plate" design example


This discussion on flitch plates is too critical.  I use flitch plates where
1)    I have limited beam depth and/or
2)    I have a deflection problem.  Instead of 3 -2X10 I might use 2 - 2x6 +
steel plate.

So long as the plate and the timber part act together (just like a built up
beam system) the bolts can be designed to allow for relative stresses etc.
Bolting along the neutral axis is sufficient if that's all the bolting
required (a bolted built up beam is not that much different).  The problem
is no more sophisticated than that.  Putting plates top and bottom, and so
on, is not the problem.  Longitudinal shear also is not an issue here.  A
flitched beam by its nature addresses only the simple problem of strength
and deflection.  Plates on one side introduce torsion considerations which
are negligible if the plate is spliced between timbers.  I agree the flitch
should go the whole length otherwise you will get all the wonderful
secondary considerations the discussion seems to be bogged down in.  As for
whether it works or not I have used simple analyses and the working member
has performed exactly as I have wished it to.

Thor Tandy  P.Eng
Victoria  BC
-----Original Message-----
From: Bill Allen, S.E. <billallen(--nospam--at)earthlink.net>
To: seaoc(--nospam--at)seaoc.org <seaoc(--nospam--at)seaoc.org>
Date: Thursday, May 14, 1998 6:31 PM
Subject: RE: Need "Flitch-plate" design example


>I totally agree and I wouldn't use this form of reinforcement unless:
>
>a.) the steel plate spans to the supports or
>b.) the plates are mounted top or bottom and attached to the wood beams
with
>lags so that there wouldn't be any slop in the bolt to wood connection.
>
>Bill Allen
>
>-----Original Message-----
>From: Al Grathwol [mailto:AGrathwol(--nospam--at)BoyleEngineering.com]
>Sent: Thursday, May 14, 1998 5:21 PM
>To: 'seaoc(--nospam--at)seaoc.org'
>Subject: RE: Need "Flitch-plate" design example
>
>
>If you aren't getting horizontal shear transfer, you're wasting steel
>plate.
>
>> ----------
>> From: Bill Allen, S.E.[SMTP:billallen(--nospam--at)earthlink.net]
>> Reply To: seaoc(--nospam--at)seaoc.org
>> Sent: Thursday, May 14, 1998 4:57 PM
>> To: seaoc(--nospam--at)seaoc.org
>> Subject: RE: Need "Flitch-plate" design example
>>
>> Even if the plates are mounted on the sides of the wood beam (instead
>> of the
>> top) and the bolts are near the neutral axis of the beam? I think not.
>>
>> Bill
>>
>> -----Original Message-----
>> From: Al Grathwol [mailto:AGrathwol(--nospam--at)BoyleEngineering.com]
>> Sent: Thursday, May 14, 1998 4:56 PM
>> To: 'seaoc(--nospam--at)seaoc.org'
>> Subject: RE: Need "Flitch-plate" design example
>>
>>
>> That IS how it gets there!
>>
>> > ----------
>> > From: Bill Allen, S.E.[SMTP:billallen(--nospam--at)earthlink.net]
>> > Reply To: seaoc(--nospam--at)seaoc.org
>> > Sent: Thursday, May 14, 1998 4:29 PM
>> > To: seaoc(--nospam--at)seaoc.org
>> > Subject: RE: Need "Flitch-plate" design example
>> >
>> > Dumb question time...
>> > So, if the load doesn't transfer to the steel plates via VQ/I
>> action,
>> > how
>> > does it get there?
>> >
>> > Regards,
>> > Bill Allen
>> >
>> > -----Original Message-----
>> > From: Ed Marshall [mailto:elmarshall(--nospam--at)HASimons.com]
>> > Sent: Thursday, May 14, 1998 3:46 PM
>> > To: 'seaoc(--nospam--at)seaoc.org'
>> > 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.
>> >
>> > Regards,
>> > Ed Marshall
>> >
>> > > -----Original Message-----
>> > > From: Bill Allen, S.E. [SMTP:billallen(--nospam--at)earthlink.net]
>> > > Sent: Thursday, May 14, 1998 6:07 PM
>> > > To: seaoc(--nospam--at)seaoc.org
>> > > 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
>> > >
>> > >
>> >
>> >
>> >
>> >
>> >
>> >
>>
>>
>>
>>
>>
>>
>
>
>
>
>
>