patternUniform excitation and timeSeries

[arbarbosa]

Hello,

If I wanted to define the UniformExcitation using timeSeries so that I could get the absolute nodal acceleration directly using a recorder, can my commands look like the following?

timeSeries Path $IDloadTag -dt $dt -filePath $outFile -factor $GMfact
pattern UniformExcitation $IDloadTag $GMdirection -accel $IDloadTag; # create Uniform excitation


For now, I have been doing my earthquake analysis by setting the commands below, which seems to be working well, but the nodal acceleration output is the relative acceleration and it can be cumbersome sometimes to add the ground acceleration to the recorder output after the analysis is complete, especially when an adaptive time stepping scheme is used.

set AccelSeries "Series -dt $dt -filePath $outFile -factor $GMfact"; # time series information
pattern UniformExcitation $IDloadTag $GMdirection -accel $AccelSeries; # create Uniform excitation

Thank you

[oleviuqserh]

Sure. To get the absolute nodal accelerations from OpenSees, add the -timeSeries option in the recorder, followed by its tag.

recorder Node -file output.out -timeSeries $IDloadTag -time -node 1 -dof 1 accel

[arbarbosa]

Thank you for the reply. It worked well.

One more question. Would the format be the one I have in the next line if I want to use one recorder to output the absolute acceleration in more than one direction, for example X and Y?

recorder Node -file output.out -timeSeries $IDloadTagX $IDloadTagY -time -node 1 -dof 1 2 accel

[oleviuqserh]

From what I can interpret from the source code, it is not possible. Only one argument is allowed with this option.

---------------------------------------------------
if (strcmp(argv[pos],"-timeSeries") == 0) {
pos ++;
theTimeSeries = TclSeriesCommand(clientData, interp, argv[pos]);
pos++;
}
---------------------------------------------------

[arbarbosa]

Thank you for the reply. I had also reached that conclusion that for now it does not seem to be possible, but by trying out on a cantilever SDOF. In an effort to reduce the number of recorders for a big structure, it might be worth adding an option that for a 3D case could look something like "-timeseries $accelX $accelY $accelZ", in which the three component rigid base accelerations ($accelX $accelY $accelZ) would be added to the relative acceleration response obtained by the node recorder "-dof 1 2 3 accel". Just an idea. Thanks

[oleviuqserh]

Instead, I think it would very useful if a new response query is added to OpenSees to compute the absolute nodal accelerations automatically, say:

----------------
recorder Node -file output.out -time -node 1 -dof 1 2 3 absAccel
----------------

Also,

----------------
recorder Node -file output.out -time -node 1 -dof 1 2 3 absDisp
recorder Node -file output.out -time -node 1 -dof 1 2 3 absVel
----------------

[arbarbosa]

I agree. Why don't you add it to future requests?

[oleviuqserh]

Asked. The request can be found here:

[url] http://opensees.berkeley.edu/community/ ... =5&t=29070 [\url]