Create the Boundary Conditions

Create a boundary condition to fix the bottom surface of the plate.

1. Select Preprocessor > Loads > Define Loads > Apply > Structural > Displacements > On Areas.
2. From the Graphics Window, select the bottom surface of the plate, as highlighted in red in the image below, and click OK in the Apply U,ROT on Areas dialog box.
3. In the dialog box that appears, enter a Displacement value of 0 for All DOF and click OK.