Hi Adi

EJMA explain about total pressure thrust, not partial as I mention.
Search this forum with "expansion bellow" you will find this concept.
I personally use this concept in our project.

I think you are working with cooling water suction line, there pressure itself will be very low so you can comfortable use untied bellow.

If pressure temperature of your line is quite high I suggest you go for another solution.

Practically speaking if your line is with cooling water service even if you use tied rubber there should not be any practical problem but you can not produce your stress report by Caesar.

In this kind of situation we check how much in piping bellow displacement without tie rod, if if it very low we draw conclusion that tied bellow in piping itself will take care of small thermal movement and finish report ignoring Caesar result on nozzle load. Because very small amount of axial movement in Caesar will create huge load.

Again yes it is very difficult to produce stress report.