How to determine the natural frequency of a structure in Robot Structural Analysis?

[umut1234X4TZP]

Hello,

I want to calculate a structure's natural frequency, but I am not sure about the results. I mean I can perform modal analysis with load to mass conversion and %90 mass participation, but it gives me a list of frequencies and periods. Is this expected behavior or on that modal analysis result list, is there a governing frequency or period? I am looking forward to finding a structure's natural frequency not frequencies. 

I reviewed How to determine the natural frequency of a structure in Robot Structural Analysis? (autodesk.com) but still it won't answer my question. 

Regards

[Krzysztof_Wasik · Accepted solution]

Hi @umut1234X4TZP 

I would say it is normal. Structures usually have more than one natural frequency

See example from network

You can define how many normal frequencies you will calculate in Robot (at least 2 should be defined).

Results for your model suggests that it is 3D structure. If you are looking for modes with maximum mass participation, then first two modes are the one you are looking for. 

Mode 1 in YZ global plane

Mode 2 in YX global plane.