If this is a large diameter storage tank (od> 120 ft) you may wish to also include nozzle deflection and rotation due to tank bulging. These displacements will be additional to the tank settlement and vary with the liquid fill level.
For instance, a nozzle that is installed (about 30" above the tank bottom) on a 200 ft tank filled up to 40' and operating at 140, can expand axially about 1" and rotate downward about 0.5 degree.
For more detail, refer to API 650, Appx P.
For the large tanks, I don't model the tank, instead I define the displacements at the vessel node(40) that are cnoded to the nozzle node(30). Finally make sure that the load cases are correctly defined and they include proper displacements.