Hi Check this log back our lead stress Engineer Steve from London done some study on this couplings. May be use fully for you.

Points to be take care

1.span to follow as per vendor span chart.
2.Check the Hydro test pressure its with stand or not.
3.which type of coupling you are using like some flexible coupling then model in Caesar. Rigid coupling not required to model.
4.Are you using for any big bore cooling water lines...
check the spans if support span not meeting change to welded elbows....

regards

akula