Christine74, I don't have references available right now, so kind of talking off the top of my head, but...
a) F&F heads for expansion joints are covered by Appendix 5, but it doesn't tell you how to calculate the stresses. You may be able to find an older analysis "Kopp & Sayre", and TEMA has an extension of it. As I recall it will use outputs from fixed tubesheet analysis as inputs to the F&F analysis, mostly in the form of equivalent pressures. Stresses in the joint are compared to allowables in Apx 5. Outputs (mostly spring rate) from the F&F head are fed back into the fixed tubesheet analysis to evaluate tube stresses, etc.
TEMA used to have a pretty nice set of integrated programs that passed the variables back and forth, and allowed you to get to the solution fairly quickly, for up to eight (I believe) load cases. That was before Part UHX. While UHX 13 does account for the joint ID and stiffness, it is not clear to me that outputs would feed directly into the TEMA F&F equations. While more simplified, I believe the Koop & Sayre analysis used only the differential expansion, or joint movement, and perhaps actual pressure as inputs.
Not sure, but Codecalc or some other modern programs may be capable of integrated analysis using Part UHX rather than TEMA fixed tubesheet calculatons.
And b), for transitions, I believe you would be justified just basing on the large cylinder thickness, with forming allowance.
Regards,
Mike
