In a Static Structural analysis, it is often better to apply a Displacement (or Remote Displacement) and measure the Reaction Force than it is to apply a Force or Moment and measure the Deformation. These two approaches are equivalent. 

The reason it is better to apply displacement than force is that there must be a non-zero stiffness at each step of the process. When applying displacement, there is stiffness to ground and it is acceptable to have a zero force reaction. If you flip to the other approach and apply a force, there is no stiffness to ground and so no solution.