RBE3 is only one of a few element types that will be used to gather interface nodes into a pilot node. RBE3 is used for Flexible connections with small deflections. MPC constraint equations will be used for Rigid connections. Contact elements will be used for flexible connections with large deflections. If you look at the ds.dat file in the solver directory, you can see what exactly was created.
You are navigating away from the AIS Discovery experience