nonlinear dynamic analysis

[mattia86]

Hi,
In the nonlinear dynamics analysis because the trend of the shift in time relative to a single node is completely positive, everything above the zero axis?. While that of relative at the relative displacement has positive and negative trends (more realistic for the dynamic analysis.
thanks

[huffte]

Hi mattia86. It sounds as if you may have a loading history which need to be baseline corrected and filtered. If you will look at the velocity and displacement histories, I suspect you will find that your displacement (and perhaps your velocity) do not return to the origin at the end of the time history, even though the acceleration history looks fine. Likely, you have large positive displacements in your integrated history. If you use SeismoSignal to baseline correct and filter the acceleration history and save the new accelerogram, I suspect you will get very similar relative results but the total results will, then make more sense.

Best regards.

[mattia86]

For the generation of accelerograms I used SIMQKE. How can I do to correct and filter accelerograms?

[huffte]

Download SeismoSignal and/or SeismoSpect.

Open your SIMQKE synthetic accelerogram in SeismoSignal.

On the Correction/Filter tab, check the boxes for "Apply Baseline Correction" and "Apply filtering".

Do not select "Show uncorrected results".

Clcik the "Refresh" button.

You time histories of velocity and displacement should come close to closing up at the end now.

Select File->Save accelerogram as-> choose your filename.

Specify this new file in your SeismoStruct loading specification.

Best of luck mattia86.

[mattia86]

Thanks, as regards the progress of the displacement seems to have resolved. Now they are more intertwined.
The problem is that I now displacement are too large in comparison with those of pushover analysis. (even 5 times the size of the target displacement pushover analysis).
In your opinion, is this normal?

[huffte]

I'm uncertain as to what you refer when you say the displacement is too large. Do you mean that you are solving a problem to which you know the answer and you are getting results 5 times higher than what you know the true answer to be?

If so, it could be that you need to refine your performance criteria to halt execution when the desired limit state has been reached.

[mattia86]

Yes, the structure by pushover analysis reaches a maximum displacement of 7 cm. With the nonlinear dynamic analysis is reached a shift of 35 cm.
I can not understand

[Stelios_Antoniou]

Mattia86,
the max. displacement is dependent on the eartquake loading you are using. Refer to the help system, in the Time-history Curves and Applied Loading tabs, and in particular note the Curve multiplier parameter of the Dynamic time-history loads.