The following zip file is a video demonstrating how to create a cylindrical structure using a finite element mesh of plate elements and apply hydrostatic loading to it.

communities.bentley.com/.../8640.Cylindrical_5F00_Structure_5F00_with_5F00_Hydrostatic_5F00_Load.zip

The associated STAAD.Pro model ( zipped ) is also attached communities.bentley.com/.../Cylinder.zip