I am considering this becasue of size constraints on the outer envelope of a beam. I realise this is an inefficient use of material, but the size constraints leave little choice.
My main question has to do with the tranverse shear stresses between the mating surfaces of the two beams. There is lots of literature about built up beams, but in this case the two beams share the same neutral axis. Will there be transverse shear between the outside of the 2.5" and the inside of the 3" that will need to be picked up by some plug welds or end welds? Is it just a matter of needing shims between the tubes at the ends so that the normal force can be transmitted and the two tubes are engaged simutaneously?
Look forward to some advice