Reply To: How to constrain a structure in a cylindrical shell while shell is not modelled?

[peteroznewman]

You can have a single remote displacement scoped to all the holes where the fastener would have held the structure to the support not modeled. Set the Behavior to Rigid. The remote point would end up in the center of the cylinder. This will be fine for most types of structural simulations.
One reason to have a remote displacement (or Fixed Joint) at each individual hole is to obtain a reaction force going through each individual fastener. You can use that information to know that the load passing through each fastener to evaluate that the fastener size is acceptable. You lose that information when there is only a single remote displacement.
One type of analysis where this type of support can be problematic is when you have a Static Structural Thermal Condition load. The rigid remote displacement constraint CTE is zero while the structure will see stress as a result of its non-zero CTE and the temperature change. If you have thermal loads, you will need to model the actual support structure so it can expand with a real CTE for its material.