absolute displacements

[Olympia]

Dear all,

Is there any other way to take absolute displacements in a time history analysis except for transforming the input motion (which is an accelerogram) to a displacement input motion (I call it ''displ.motion''), run the analysis exciting with the accelerogram and simply add (1) the relative displacements that I take from the OpenSees with (2) the displacements (''displ.motion'') that I defined?

Thanks a lot in advance,
Olympia

[fmk]

could you rephrase the question.

[Olympia]

I mean that if I use the following command:
recorder Node -file nodesD.out -time -node 1 2 3 4 -dof 1 2 disp;
I will take the relative displacements, right?

What if I want to plot the absolute displacements?

Many thanks in advance,
Olympia

[fmk]

the recorder command will return the displacements at the nodes .. if the load pattern was a uniform excitation one, they will be relative .. if a multi-supppor pattern they will be absolute .. if they are relative and you want absolute you can do this by post processing .. an alternative is to split the output ino 2 files, dof 1 to oe, dof 2 to the other .. to the recorder command add the time series that defines the ground displacements and the recorder will add these to the absolute one to give the total.