Just to chime in as I have done more expansion joint then I would like...

On one particular job, I calculated the full thrust force in CAESAR II by setting the ID of the EJ so the program would calculate the force. Then in the results via excel I "corrected" the results for pressure thrust by removing the pressure times the open area of the nozzle. This gave very satisfactory results while maintaining all the forces in the pipe.

Thanks,
Duncan