Hi Dr. Day,

Good morning. Thank you for your response.

We were also exploring the frequency range damping (with the deform option, as we had rigid body modes) that you mentioned. We found that for our case, a frequency ratio of 10 (Fhigh/Flow = 10) is more appropriate. We also wanted to implement a damping coefficient of 0.05. However, with some simple analysis we found that the response was accurate for 1-2% damping when using the keyword *DAMPING_FREQUENCY_RANGE_DEFORM.

Now, considering all of it, what can be a good approach to apply 5% or 10% damping for our model? We were trying to do some nonlinear analysis by imposing earthquake motion at the base of the system. Do we need to play with the stiffness of the system as the manual mentions?