How to Obtain Damping (or Stiffness) Matrix?

[staniser]

Are there any way to obtain or record the damping (or at least stiffness) matrix of a system in OpenSees?
During time history analysis, I need to get what damping ratio does OpenSees calculate for each mode when using mass and stiffness proportional Rayleigh damping command.

[vesna]

There is no recorder for stiffness and damping matrix. You can do a simple example manually and using OpenSees to figure it out.

[staniser]

Thank you vesna, I will work on that.