timber header fish-plate design
timber header fish-plate design
(OP)
An unusual construction for a timber header for a room addition to an older duplex residential building. The header is built from two 2x8's and a 3/8" steel plate between the boards. Is it possible to ratio the modulus of elasticity for steel and wood to get an equivalent area of wood and then check the allowable stress and deflection? I am using a timber design computer program to solve the problem.






RE: timber header fish-plate design
RE: timber header fish-plate design
I agree with PSelm, in addition, use the properties of the wood for lateral support of the plate. In affect what you have is an I-Joist, with the steel being the web and the wood being the flanges.
RE: timber header fish-plate design
if the steel plate and the 2x8's are both 7.25 in high and
E wood = 1.5 x 10^6 psi
E steel = 29 x 10^6 psi
Then the the 0.375 inch steel plate can be assumed to act as a 7.25 in (high) x 7.25 in (wide) wooden member. Of course the composite member that you would analyze would include the 2x8's to make the eqivalent (wood) composite member 7.25 inch (high) by 10.25 in (wide). Also as PSlem mentioned you have got to limit the actual stesses to acceptable values for both the wood and the steel respectively.
Chances are you cannot ignore the wood for shear stress calculations, it often provides almost all bearing since the steel plates bearing area is very small and is usually negligible.
All of this assumes adequate connection (bolting?) thru the wood / steel plate.
RE: timber header fish-plate design