How do you explain such a moment distribution as seen in figure 1?
It looks as if the cantilevered part of the surface is supported at its outer edge, thus resulting in a moment under the concentrated load.
This moment distribution results from the plate resistance.
The concentrated load acts on only at a part of the surface, so that the entire cantilever surface deforms uniformly downwards.
The greater the distance from the load, the smaller the deformation.
The adjacent regions therefore act as a support for this part, which explains the moment distribution.
Only if the line load is relative to the entire width, you obtain the expected moment distribution. It corresponds to the a distribution for a member.
Please bear in mind the different structural behavior of surfaces and members when designing in RFEM and RSTAB.
Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements