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Re: "Flitch-plate" design

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Dennis

This is exactly how I approach this problem.  It is not that much different from other composite types of analysis.  As in other hybrid systems it is fine until second order effects such as extreme deflection and strain occur.  I have found that most uses do not invoke such conditions and I am comfortable with using that simplified method.  Fastener detailing is the key if you are concerned with the assumptions.

Thor

-----Original Message-----
From: Dennis S. Wish <wish(--nospam--at)cwia.com>
To: seaoc(--nospam--at)seaoc.org <seaoc(--nospam--at)seaoc.org>
Date: Friday, May 15, 1998 12:12 PM
Subject: RE: "Flitch-plate" design 


>I could not find them in these references either. However, I did find one in
>the book "Structural Design in Wood" by Judith J. Stalnaker and Ernest C.
>Harris. The design examples assume concentricly placed stiffer member
>(sandwiched). It is also refered to as a "Vertically Laminated Beam". It has
>one caution:
>"To design any of these types, the fransformed-section method must be used.
>The transformed section is an imaginary section of stiffness equal to that
>of the actual reinforced beam. Its dimensions and properties are found by
>imagining the steel area to be replaced by an elastically equivalent area of
>wood. The elastically equivalent area of wood is the area of steel
>multiplied by the ratio of the modulus of elasticity of steel to that of
>wood.
>Designers should be cautioned that the variations in modulus of elasticitiy
>of wood affects the assumptions made. The coefficient of variation of E in
>wood is around 25-30%........The action of the reinforced beams is based on
>the fact that the deflected shape of the wood and steel portions are
>compatible. For the flitch beam, for example, both the wood and the steel
>plate bend to the same deflected shape. If the loads include long-term
>loads, a lesser E-value should be used for the wood." Page 291-292
>Published by Van Nostrand Reinhold - 1989.
>
>Dennis Wish PE