The Simply Supported node adds an edge condition that constrains the displacement in the direction perpendicular to the shell. The in-plane rotation perpendicular to the edge is also constrained. Optionally you can constrain the in-plane displacements.
Select Along edge to constrain the in-plane translation along the edge.
Select Perpendicular to edge to constrain the in-plane displacement perpendicular to the edge.
) and select Advanced Physics Options. 
