FREQ command does not allow enough data points

[hodge1818]

I am working on a spectrum analysis for a water tower in order to see how it would respond to an earthquake.

I've managed to get the earthquake data in terms of frequencies and acceleration responses but I have about 2000 data pairs I would like to input.

I'm ready to fill out the FREQ and SV values but it only allows a maximum of 20 points.

Is there any way I can get all 2000 in there?

 

[hodge1818]

After doing some more reading, would it be better for me to do a transient dynamic analysis and input the data as a displacement table? Might that allow me to get all of the data in there? I realize I would need to convert the data into displacement and time somehow but I'm sure I could figure it out.

 

[cbrn]

Hi,
if you have a time-history, then you'd better perform a transient analysis; if you have spectra, then you'd better perform a spectrum response analysis. If you deal with spectra, generally it is easy to "simplify" the spectra to fit into a 20-points table. At least, this is what I've done several times with the italian accel spectra.

Regards

 

[hodge1818]

Thanks cbrn. I looked into it more and actually found a book about earthquake engineering and it helped me figure out the design spectrum for earthquakes which was much more simplified with about 7 frequencies.