flitch plate beam

huangyhg

flitch plate beam
how can i analyze acomposite flitch plate beam, 20 ft. long, 3/8 steel plate by 9 in. sandwiched between 2 - 2x12,bolted with 3/8" carriage bolts on 12" centers?  by hand, no software.  need it this week.
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the load is shared in proportion to the stiffness of the two elements, i.e. the product of e x i.
in addition, shear flow between the different materials must be calculated.  if the steel plate is not dead center of the 2x12's and the 3/8" bolts also are not at the center, number of bolts have to be calc'd to justify that the load can be shared based on the stiffnesses of each pieces.
conservative answer - consider the steel plates as doing all the work, forget about the wood.
pylko, nice answer.
steel plate should only be designed to carry bending only.  reactions at each end (bearing) should be checked with 2-2x12's.
see my thread here on flitches.
inspector jeff in florida
there is a two-page article in the september 1989 issue of civil engineering magazine on flitch beam design.  the article is by j. d. wiesenfeld, who was (is?) a professor at the new york institute of technology's school of architecture.
thanks guys!  really preciate the help on the flitch plate beam. this was a garage door lintel that the building inspector turned down.  i was asked to look at and make it work.
my first time.  it's the best thing that has happened for engineers.
thanks again.
as stated before you may design plate to take full bending. space bolts to provide lateral support to steel plate. also, if considering both wood and steel, bolts must be sized and spaced to transfer load to wood side plates...good luck.
design the steel plate as a beam and forget the 2x except to distribute the bearing end stresses..
inspector jeff in florida