To adequately perform the required dynamic analysis, the analysis must include the dynamic effects of the soil/foundation/rotor assembly.  The bearings, bearing supports, foundation and soil all contribute to the system dynamic response caused by the fan rotor unbalance forces.  This GT STRUDL analysis for the I.D. fan foundation design for Plant Bowen Units 3 and 4 involves the combination of these various components and their unique dynamic properties.

The final GT STRUDL model included the dynamic properties of the fan model and the soil/ foundation interaction analysis with a model of the concrete foundation.  The foundation was modeled using 3-d solid elements with massless rigid links attached to the c.g. of the soil/foundation, as well as to the bearings of the rotor model, the coupler, the fan housing and to the motor.  This combined model was created to simulate the entire soil/foundation/fan system and to analyze for resonant conditions as well as for maximum vibration amplitudes at the bearing.

The complexities of this model provided an opportunity to utilize many of the more advanced features offered by GT STRUDL.  These include:  the ability to combine member types, the input of damping properties using matrix damping and the ability to input stiffness properties in matrix form (for oil film, pedestal, bearing, soil).  The analysis was performed for an operating range of 20% to 100% of the top operating speed.  With the stiffness and damping characteristics defined for the various frequencies, a transient analysis was performed to obtain response displacements which were evaluated against the peak-to-peak allowable of 0.125 mil per ounce of unbalance.

The purpose of this presentation is to discuss the optimization of the GT STRUDL capabilities to be used for the analysis of this combined system.  The GT STRUDL support group worked closely with me to resolve several technical issues.  These issues and the basis for the analysis approach will be presented.