The purpose of the Flexible Foundation node is to model the effect of the flexibility of the foundation on which the bearing is mounted. In this case, the motion of the foundation is not known a priori, rather it is solved for. Here, the inputs are the stiffnesses, ku and kθ, and the damping constants, cu and cθ. If the coupling between the foundation’s translational and rotational motion is considered, the inputs kuθ, kθu, cuθ, and cθu are also needed. The contribution to the virtual work is