Rotordynamic critical speeds and lateral natural frequencies are dependent on housing and foundation mass and stiffness properties. For equipment with complex geometries it can be difficult to predict the effect of the support stiffness.
To accurately predict the shaft lateral natural frequencies where complex structural geometry is involved, it is necessary to have an accurate model of the support structure. This is accomplished by creating a three-dimensional (3-D) finite element model (FEA) of the structure. Mass and stiffness properties for the structure can be calculated and used in a dedicated rotordynamic analysis package, or the shaft can simply be added to the 3-D structural model using spring, damper, and beam elements.
