The baseplate is fixed on the ground but allowed to expand in all directions freely, achieved via a frictionless support on the bottom surface of the baseplate with a fixed support on the center node of the baseplate bottom surface:

Figure 66.6: Overview of Boundary Conditions and Loads

This figure illustrates the bottom surface with the frictionless-support and fixed-support boundary conditions that constrain rigid body motion:

Figure 66.7: Bottom Surface

A gravitational acceleration is applied so that frictional forces between the bridge and the substrate prevent rigid body motion. The temperature of the part changes with time).