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Modal time history analysis
Posted: Tue Sep 24, 2024 11:28 pm
by jfhuang
Hello everyone, does anybody know how to do a linear modal time history analysis in OpenSees? This will be useful in understanding the dynamics of the structure and modal contributions. I know we can do a response spectrum analysis but a time history is more of what I need. Thanks a lot for the inputs.
Re: Modal time history analysis
Posted: Wed Sep 25, 2024 5:32 am
by kesavapraba
Hi, I am not aware of any direct method available in OpenSees. However, you can still achieve it by some custom TCL script or extenal numerical platform, like MATLAB and Python. After developing your model, you can obtain mass and stiffness matrices as well as modal properties (frequencies and mode shapes) from OpenSees. With these information, you can write the model from physical into modal coordinates and then you can conduct time history analysis on each SDOFs and subsequently back assemble the response in physical coordinates - any structural dynamics book can help to understand this step. Please note that STKO also provides Python API in post-processing, you can explore this possibility to assemble the responses of SDOFs.
Re: Modal time history analysis
Posted: Wed Sep 25, 2024 7:47 pm
by jfhuang
kesavapraba wrote: ↑Wed Sep 25, 2024 5:32 am
Hi, I am not aware of any direct method available in OpenSees. However, you can still achieve it by some custom TCL script or extenal numerical platform, like MATLAB and Python. After developing your model, you can obtain mass and stiffness matrices as well as modal properties (frequencies and mode shapes) from OpenSees. With these information, you can write the model from physical into modal coordinates and then you can conduct time history analysis on each SDOFs and subsequently back assemble the response in physical coordinates - any structural dynamics book can help to understand this step. Please note that STKO also provides Python API in post-processing, you can explore this possibility to assemble the responses of SDOFs.
Hi Prabakaran, I was trying to figure out whether there is a more convenient way of doing it instead of performing modal decomposition and mapping between nodal DOFs and mass/stiffness/damping matrices myself externally. Thanks for the response and suggestion!
Re: Modal time history analysis
Posted: Thu Sep 26, 2024 8:33 am
by kesavapraba
Yes, I understand that. We can have an answer if any of our forum members has an experience in it.
Re: Modal time history analysis
Posted: Wed Oct 02, 2024 8:51 am
by STKO Team
No, OpenSees only has direct integration analysis