seismic waveform simulation

[srmech]

Hi All,
I'm working on the issue of the simulation of the seismic waveform using a series of harmonics in a frequency range of interest.
The big problem I have is to find the equivalent magnitude of the acceleration in frequency domain.

I would appreciate any comment on this issue.
B.Serban

 

[tomirvine]

I can probably help you. I have written a number of software programs for various types of shock simulation.

Can you give more information about the type of waveform that you are trying to simulate? Is there some specification, like a shock response spectrum?

Tom Irvine

http://www.vibrationdata.com

 

[srmech]

I have to clarify my inquire.

I'm not looking for a way to synthesize a seismic record because I have already one. Bellcore GR063 provide a synthesized waveform that should be applied on the shaking table, and this waveform is the base for the required response spectra for 2% damping presented in the same standard. As you know a response spectra refers to a series of independent SDOF (mass-spring-damping) and not necessarily to a specific structure.

So, I have the seismic waveform (time domain) that I can transform in frequency domain (FFT) and find the magnitude vs. frequency. If I used a series of harmonics of the same magnitude and frequency, the response isn't the same because the duration is different. If harmonics are applied, the response tend to develop to the max magnitude (for 2 octave/min or less- magnitude is about 90% of max value-IEEE344). On the other hand, the seismic duration is very short (30s for 1-50 Hz range-about 5 octaves) and the magnitude is less developed. The issue is how can I find an equivalent magnitude of harmonics such as the structure response (like acceleration) is similar with the one during seismic event.

If this equivalent magnitude can be found, then a seismic test can be simulated with sine seep survey test.

Is any material available that you can point out?
Thank you,
B.Serban