Loadings

To apply gravity, go to

Preprocessor --> Loads --> Apply --> Structural --> Inertia --> Gravity

Enter -1.0 for z-axis acceleration

The red arrow indicates the direction of z axis acceleration.

To apply the displacements, go to

Preprocessor --> Loads --> Apply --> Displacement --> On Nodes

Now, let Uz = 0 for every node on the top surface.

Then let Ux = Uy = 0 at the middle point of the top surface.

In order to prevent rotation about z axis, specify zero y displacement

for at least one node along x axis.