fletch beam properties 5

[munchscrunge]

thread507-1083 c16 and c24 sw timbers will take stress of 5.3n/mm2 and 7.5n/mm2 respectively.What would this be increased to ,by the addition of a 12mm ms plate sandwiched between two members.

 

[DST148]

If you are looking for an answer, I don't have one. Usually books on Strength Of Materials have one chapter devoted to beams of different materials. Book by F.L. Singer has a solved problem something similar to the one you have posted.

 

[Lion06]

I'm not sure I understand your question. The addition of the steel "flitch" (not fletch) plate, doesn't increase the allowable bending stress in the wood, it just takes some of the load (and, therefore, some of the stress) away from the wood and into the steel.

 

[Ron]

munchscrunge....Lion06 is correct. You have to consider flitching as a composite process, not an independent process. Once you connect the steel and wood together, they will each feel stress relative to their respective mechanical properties.

 

[dhengr]

Munchscunge:
The various members (steel or wood) share the load on the beam in proportion to their relative stiffnesses, both moment of inertia and modulus of elasticity. Once they are joined together, they will all deflect the same (as one beam) under the load and the trick is to connect them together so as to cause the required force transfer between them and at the same time not overstress any of them. As mentioned above by DST148 any number of Strength of Materials or Structural Engineering texts will lay this design process out in more detail. The most complicated part of the design is this force transfer interconnection of the members, and the shear and end bearing details.

 

[MiketheEngineer]

It is a "flitch" beam. It has been discussed numerous times on these forums - search them and you will find all the answers you want - and more!!