Error after adding diaphragm interaction

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natalialioe
Posts: 4
Joined: Wed Aug 11, 2021 12:17 pm

Error after adding diaphragm interaction

Post by natalialioe » Wed Aug 11, 2021 1:49 pm

Dear STKO Team,

I am studying the friction pendulum bearing modeling and got few questions to ask as follows:

I simply use the base model provided in the website https://asdeasoft.net/?webinar#019 and delete all the geometries and rebuild it. I stuck on the modeling when I add the diaphragm. For the "WithoutDiaphragm.scd" is runnable, but for the "WithDiaphragm.scd" is not runnable, it occurs an error "starting vector is zero".
Model.rar
(247.46 KiB) Downloaded 9 times
error.png
error.png (41.13 KiB) Viewed 199 times
How do I fix the modeling? And how to prevent this error later on?

Thank you very much

Best regards,
Natalia Lioe

STKO Team
Posts: 737
Joined: Tue Oct 29, 2019 8:45 am

Re: Error after adding diaphragm interaction

Post by STKO Team » Mon Aug 23, 2021 9:29 am

You assigned 3 masses (Mx My Mz) to 2 nodes, so you have a total of 6 free DOFs with mass (dynamic DOFs).

The default solver in Eigen is the -genBandArpack. This solver is good for large problems (dense or sparse) but can give you at most N-2 eigenvalues, where N is the number of dynamic DOFs.

You requested 3 eigenvalues.

This is fine without a rigid diaphragm, because 3 < N-2 (4).
When you add the rigid diaphragm, the 2 nodes with mass are constrained to the master node, and so you end up with 4 dynamic DOFs (mx and my are constrained, + 2 mz components).

So in this case you need to use the -fullGenLapack solver, which can give you all eigenvalues, but works only for small problems.

Another issue is that you need to FIX the Uz,Rz,Ry DOFs of the master node, otherwise your structure is un-stable

natalialioe
Posts: 4
Joined: Wed Aug 11, 2021 12:17 pm

Re: Error after adding diaphragm interaction

Post by natalialioe » Sun Aug 29, 2021 3:06 pm

Dear STKO Team,
Thank you very much for the reply, it's very helpful.

Best,
Natalia

STKO Team
Posts: 737
Joined: Tue Oct 29, 2019 8:45 am

Re: Error after adding diaphragm interaction

Post by STKO Team » Mon Aug 30, 2021 7:57 am

You are welcome!

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