How to extract stiffness and mass matrices?

[HassanF]

Hello,

Is there any way to extract initial stiffness matrix and mass matrix of a structure in OpenSees?
Also, if it is possible to have tangent stiffness matrix of the structure in each time step of a transient analysis?

Thanks,
Hassan

[gor]

Perhaps this is of interest?

http://opensees.berkeley.edu/wiki/index.php/PrintA

[HassanF]

Thank you Gor. I tried to use printA, but does not work.

[fmk]

did you notice the part about the FullGeneral system being required.

[HassanF]

Thank you fmk, I used FullGeneral system, it is working.
I see that at the case of transient analysis, the result of printA will be some combination of mass and stiffness matrices. What is the coefficients?

[fmk]

that is something you can figure out .. look at the theory for the integtaion scheme you are using and knowing dT and factors you applied you can determine the ratios.