Calling modalDamping when modal properties change

[taycamste]

Hello,

It's not clear to me from the paper by Chopra & McKenna or the documentation whether the modal properties are updated during nonlinear response history analysis when modalDamping is invoked. Does OpenSees update the mode shapes used to constructing the damping matrix each iteration? Or must one specify both eigen and modalDampnig within a loop at each step (e.g., as one would do with tangent-stiffness proportional Rayleigh damping?)

Thanks,
TCS

[mhscott]

Mode shapes are not updated automatically. You have to put eigen inside a loop like you said.

[taycamste]

Thank you Michael, perhaps this is obvious but must the modalDamping command be invoked after eigen in each loop as well?