Dear all

I am doing CAESAR II to analyze piping system with slip joint of district heating piping in culvert.
I modeled slip joint manually also input pressure thrust as F1.

The key point is it.
For load case setting, I am wondering if pressure thrust, F1, added manually in sustained load case.

SUS = W+P1+F1
SUS = W+P1

Which is correct??

If you provided your pressure thrust forces as a load F1, then you should include F1 in the SUS (and operating) load case.
If you defined your slip joint as an expansion joint (XJ) and you entered an effective ID for your XJ, you need not define F1 to model the thrust because this load (the thrust force) will be included in the P1 load component.