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Nice idea. Thank you.

I have used Rayleigh damping in several ways such as Rayleigh command, region command and using in Newmark integrator command. Then I have changed the value of them by 100, but the natural period of structure calculated by Eigen command did not change. It seems that the Eigen solver even do not cons...

Yes I have tried a range of 1E+5 to 1E+7 which reduce the maximum drift of structure to less than half, and also I have modeled one of the samples of a passive control book in which the period of structure before and after using dampers is given, and in there I have get same results. About the Rayle...

Dear Silvia I have done it, but no changes occur. In the OPENSEES analyzes the natural period does not correlate to dampers constants! Is it possible that in evaluating natural period of structure it does not consider the viscous damper elements? I have put the dampers definition below: # dampers se...

Dear all
I have used some dampers in a steel moment frame using the viscous material and truss elements, but the natural period of structure calculated by OPENSEES did not change. My question is that what is wrong and how could I solve this problem?

Dear Silvia Thank you for your soon replying. I have analyzed a 2 story steel frame under Morgan Hill 57383 earthquake record while some gravitational load applied to the frame too. And I have get this eigen values from the eigen command during the analysis just like below: 0 3.568996e+001 . \ . |-P...

Hi I did an eigen value analysis on a simple 2D steel frame and I have get negative eigen values during 0.1 second of my time history analysis which is applied 40 seconds. On the other hand the other recorder objects like element recorders did not stop recording the status of the elements. My questi...

Dear silvia
Thank you for your reply. But still I don’t know how I can calculate them. The eigen vectors which opensees gives in outputs are normalized based on the mass participation ratio. Please tell me how I can calculate them without adding some functions to opensees source if there is any way.

I need to calculate modal mass participation ratio on each step of time history analysis. I don’t know if there is any way to calculate it from opensees outputs. Pleas tell me if there is any way.