Apply Boundary Conditions

Create boundary conditions that minimally constrain the movement of the bottom surface of the plate and prevent rigid body movement.

The boundary conditions are shown below.

boundary conditions

Select Preprocessor > Loads > Define Loads > Apply > Structural > Displacement > On Areas.
From the Graphics Window, select the 2 bottom surfaces of the plate and click OK in the Apply U,ROT on Areas dialog box.
In the dialog box that appears, enter a Displacement value of 0 for UY and click OK.
Select Preprocessor > Loads > Define Loads > Apply > Structural > Displacement > On Keypoints.
Select point "A" and set UX and UZ equal to 0.
Repeat steps 4 and 5, selecting point "B" and setting just UX to 0.