I have a problem to calculate the natural frequencies for a rigid frame founded on springs by using the dynamic module of Caesar.

Running the dynamic analysis with activated translational and rotational masses it always leads to very low natural frequencies far below 1Hz. I can`t find any mistake in my Caesar input file.

I did a calculation of the natural frequencies by myself and it leads to reliable results showing natural frequencies starting from 3 Hz (see attached *.pdf)

May there be any internal mistake in Caesar when the units are defined, which causes too low frequencies?

I attached the Hand-calculation and the Caesar input-file. Maybe you could help me

Best Regards,

Rick

Our default, lumped mass approach does not include rotational inertia in the mass model. You have rotational inertial defined in your input. To properly apply that mass, you must specify CONSISTENT mass rather than LUMPED mass in the Control Parameters.

You can check how CAESAR II places mass by reviewing the Included Mass Data report.