Answer:
There are three options you can select from.
- Undeformed system: The deformation is related to the initial structure.
- Displaced parallel surface: This option is recommended for the surface with elastic supports. The deformation uz,local is related to a virtual reference surface displaced parallel to the undeformed structural system. The displacement vector of the reference surface is as long as the minimal nodal deformation within the surface.
- Displaced user-defined reference plane: If the supports of a surface deform very differently, an inclined reference plane for the designed deformation uz,local can be defined. This plane must be defined by three points of the undeformed system. The program determines the deformation of the three definition points, places the reference plane through these displaced points, and then calculates the local deformation uz,local.