tangent stiffness matrix

[adelm]

Hi everyone,
I would like to extract (output) tangent stiffness matrix in a static analysis? Can anyone help please?
Thanks

[fmk]

use a FullGenSystem and then use the printA command:

http://opensees.berkeley.edu/wiki/index ... tA_Command

[adelm]

Dear Frank,

Thanks for your reply. Let me take the problem one step higher, I would like to grab the initial stiffness matrix and then apply a set of load and get the new stiffness matrix. Then subtract the first one from the second to get geometric stiffness matrix. Do you think that's a possibility? Could you please guide me on if it is possible, then what will be the relationship between the subtracted matrix and geometric stiffness matrix? Is the a definite multiplier of that?

Thanks again,

Adel

[fmk]

it is .. just do an alnalysis with 0 load to get the first one place in 1 file (you might even want to specify a -initial with the algorithmm) .. do your analysis and save the results for the tangent to another file .. use matlab or even tcl to load the 2 files, compute the difference and save to a third file.

[adelm]

so then do you think if I write a code to do eigenvalue analysis for the initial stiffness matrix and the subtracted stiffness matrix (=geometric stiffness matrix), that would give me the buckling load of the system?
Thank you

[cexuhan]

Hi Adel

Did you solve this problem? I have the same trouble now.

Thank you

Xu

[konveksikaos]

Did this good answer? Btw thxs for solved it problem