Plane load cannot be applied to the plate elements in curved alignment.
Firstly, the plate elements on which the loads are applied have to be defined as a Structure group. Then, to apply plane loads on the curved surface, select 'Group' in the 'Element Section' under 'Assign Plane Loads.'
When the plane load, which is defined with 'Define Plane Load Type', is applied to the plate elements on the curved surface using the 'Assign Plane Loads' function, the following error message is displayed and the load may not be applied.
If 'Element Selection' of 'Assign Plane Loads' is selected as 'Elements on the loading plane', then loads are applied to the elements existing on the Loading Plane. However, if it is applied to a plate element on the curved surface, as shown in the figure below, an error occurs because there are no elements on the plane where the load is applied.
In such cases, the error can be solved by defining the plate element as a 'Structure Group' and selecting 'Group' in the 'Element Selection' of 'Assign Plane Loads'.