Torsional Vibration of a plate and a frame attached to a bar element

[Bharathsf]

I have modelled a circular plate attached to a frame using rigid elements. I have attached 2 cbar elements on either side of the frame and i have rigidly constrained the bar elements. I ran the file and got a natural frequency of 3Hz. I am not sure if the answer is correct. How to calculate the natural frequency using hand calculations for the model so that I can verify.I have attached the dat file of the model.
The radius of the bar element is 0.8845 mm so that the torsional stiffness of the bar will be 5000N-mm.


Please help me

Bharat