How can I plot a trendline that follows the peaks a time-history data set (accelerogram)?

Hello all,

I'd like to calculate the damping ratio of a structure based on acceleration data.

To do so I usually take the logarithmic decrement of a nice sinusoidal wave. However, in certain cases I obtain waves that do not allow me to do so easily thus I would like to create a trend line that follows the peaks as shown in the PDF attached. With this curve I could estimate the overall damping of the structure.

The image below shows graphically what I would like to do.

Thank you in advance

[dpb]

doc envelope

Answer 1

[Star Strider]

The envelope function could do what you want.

Another option is findpeaks, with the appropriate name-value pair arguments.

Both are Signal Processing Toolbox functions.

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[Joshua Castellanos]

Thank you, I'll give it a try and update the status of my question accordingly.

[Star Strider]

My pleasure!

If I had the signal itself, I could provide actual code. It might be necessary to use a lowpass filter first to eliminate the high-frequency parts of the signal. Determine the best cutoff ffrequency by first performing a Fourier transform of the signal with the fft function.

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