Unbalanced Response of a Large Rotor-Pedestal-Foundation System Using an Elastic Half-Space Soil Model

The unbalanced response of a large rotor-pedestal-foundation system using an elastic half space soil model was determined. The effective stiffness and damping terms between the foundation and soil were determined from the elastic half space soil model. The rigid body equations of motion of the foundation were derived subject to applied forces from the bearing-support structure and from the springs and dashpots representing the soil. An impedance matrix representing the relationship between the bearing-support structure forces and the corresponding displacements was then derived and matched with the finite element model of the turborotor system. The analytical results of this investigation were compared with test data from a recirculating gas fan at a power plant installation. There was very good agreement between the analysis and the test data. This is the first time a realistic coupling of rotor models and foundation-soil models has been accomplished. This method of analysis should be the basis for the design of rotor-bearing-foundation-soil systems.