Should I extract it from output that I find from natural period and mode shape?
Dear Muhammad Ichsan:
If I correctly understood your question, you want stiffness matrix and mass matrix of the model that you built. Yes you can. But they are not extracted in table output. I extracted them once. Hopefully my experience can benefit you:
1. Set advanced analysis.
2. Set the case that you intend to output (Corresponding to the matrix you want)
3. Run the analysis
4. Find files with extensions of ".TXK" and ".TXM"
The file ". TXK " is the stiffness matrix file. The file ". TXM " is the mass matrix file.
The first and the second columns are number of degree of freedom, respectively. The third column is the stiffness or mass value.
Please find attached MKguide.pdf, which includes illustration in it. Sorry for my SAP2000 is in Chinese, please find those buttons in the same place in your SAP2000. If it is not clear, please feel free to contact me.
Best regards.
Bowei.
Thanks for your answer Mr. Bowei,
I have found it, but just not according to my expectation.
It seems that sap 2000 software have stiffness matrix value is composed of the material but not arranged according to the finite element equation rules.
I compare the result with my manual calculation in matlab.
Dear Muhammad Ichsan:
Sorry for my answer just now did not solved your question. May I ask:
1. What the arrangement of DOF(Degree of freedom) do you expect to have?
2. Are you going to used it in Matlab?
To my knowledge, in SAP2000, each node has 6 DOF, including 3 translational DOF and 3 rotational DOF.
Best regards,
Bowei
1. I use equation for truss element based Finite Elemet Books (Logan), I attached here (captureJPG-global matrix), so if I have 1 truss element member it is consist of 4 x 4 Matrix (each join has 2 DOF).
2. Yes, I compare SAP 2000 and matlab
I have tried that SAP 2000 can be set with 2 DOF also sir.
Dear Mr. Bowei
So far my benchmark that the values between sap 2000 and matlab are same in the value of the natural period with a little error
-Ichsan
Dear Muhammad Ichsan:
Thank you for tell me this, I think this might work:
1. Check if your model is 2D or not. In analysis setting window, you can select 2D analysis.
2. Delete uncessary DOF such as 1 out of plane translational DOF and 3 rotational DOFs. You need to delete the corresponding columns and rows.
With each node has 6-3-1=2 DOFs, each node will only have 2 translational DOFs.
However, due to my limited knowledge, this is the only way I know. It seems tedious to do this. Hopefully you can find a better one.
Best regards!
Bowei
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