Description: The rotordynamic load (ROTDYNF) is a special load type that can be used to study the vibrational response of three-dimensional models of axisymmetric structures, such as a flywheel in a hybrid energy storage system, that are spinning about their axes of symmetry in a fixed reference frame. This is in contrast to the previously available centrifugal loads, Coriolis forces, and rotary acceleration loads, which are formulated in a rotating frame. The intended workflow for the rotordynamic load is to define it in a nonlinear static step to establish the centrifugal load effects and load stiffness terms associated with a spinning body. The nonlinear static step can then be followed by a sequence of linear dynamic analyses (such as complex eigenvalue extraction and/or a subspace or direct solution steady-state dynamic analysis) to study complex dynamic behaviors.