Mass and Stiffness Matrix

[alirezaarab]

Hi

I am modelling a 3-D frame in OpenSEES is there any way to record Mass matrix and Stiffness matrix in each step of analysis??

Thanks

[fmk]

yes. it requires a bit of work using the printA (as printA will only print the contents of the A matrix and if transient analysis, this is some combination of K and M, so you would either have to know M, the factors and determine K or you might be able to switch analysis from transient to static and back again)

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

[alirezaarab]

Thanx

[wuhaoshrek]

fmk wrote:
> yes. it requires a bit of work using the printA (as printA will only print
> the contents of the A matrix and if transient analysis, this is some
> combination of K and M, so you would either have to know M, the factors and
> determine K or you might be able to switch analysis from transient to
> static and back again)
>
> http://opensees.berkeley.edu/wiki/index.php/PrintA

Hi fmk
Why nothing happened when I do printA -file $dataDir/AMatrix.out;

[mhscott]

'printA' only prints to standard output

[alirezaarab]

I have problem too

OpenSEES does not recognize this command

[alirezaarab]

I modeled 3D frame with 1 story, 1 by in y direction and 1 bay in z direction after running one step of push over analyze, using printA it gives me a 86*86 matrix but my frame have 48 DOF and should have stiffness matrix of 48*48
I am confused can any body help me???

[sjavadinasab]

@alirezaarab: I tried this command but OpenSees just ignores it!!!! It looks as though you had a similar problem. How was it solved? Why nothing happens when I do printA?

[fmk]

unless you are using lagrange multipliers the dof matrix size should be the same as the number of free dof. issue the command 'print node' and look at the ID of the nodes to see why you have so many dof.

[fmk]

and you see no outut unles you have a full matrix type chosen, re-read the command for printA