You can install what is called a "roller" restraint from one of the automatic-type fixtures. However if you are using shell elements, that might not work (depending on the selection).
If that does not work, use the "old", tried and true method of applying restraints: Choose the "Advanced" option in Fixtures Property Manager (PM). You can select a reference plane. For example, choose the pipe or flange end face for the restraint, then choose a plane that is parallel to that face. There should be three component directions available to select in the PM. Choose the one that is normal to the plane and put a zero (0) value in there. That will hold the end face of the pipe from translating normal to itself, but will allow radial expansion and translation in the plane. The symbols should look like 3D arrowheads placed normal to the surface (indicating a restraint in that direction, in this case zero). Hope that helps. -Tony