Yes it is. Define an element with the length of the pre-compression and then define the material as "(19) Cut Long". It's very unusual to pre-compress and an expansion joint, normally they are pre-extended so that when the line heats up, the expansion joint grows towards the neutral length. Are you dealing with a cryogenic line?

Dear Sir,

If you’re doing a detailed model of an ILPB joint, then I would recommend just one pre-extension at the inlet or outlet of the joint. This will have the effect of pre-extending the line bellows and pre-compressing the balancing bellows.

Due to the complexities of an ILPB and the problem of large rotation of the restraint rods, I generally recommend you use a simple single zero length expansion joint to represent the joint. You would then manipulate the spring rates and effective diameter to represent the joint. The axial, lateral and torsional spring rates would be the overall spring rates of the entire joint. The rotational spring rate would be rigid (10e^6) and the effective diameter would be zero. The overall length of the joint should be set to ambient temperature to represent the thermal growth that is trapped and resolved internally under the tie rods. The results will be accurate for your system. However, you will have to manually have to add the axial growth under the tie rods to the design movements of the joint.

If you have further questions, I suggest you contact me directly at pipesol@connectnet.com