Record Modal Properties

[suuzie]

Hi,

I wonder if we can record modal properties (modal displacement or modal period) per each time step.
For example, the bridges with nonlinear materials have different period when the structure enters inelastic response under strong earthquake motion.

If this is possible, how can we write the recorder command?

Best,
Suuzie.

[fmk]

you can issue the eigen command at each step and record the eigenvalues or eigenvectors .. OpenSees does not calculate modal particpation factors or anything else.