摘要(英) |
When it comes to Structure Health Monitoring, we always use the modal parameters to recognize the difference of the output signal. In the past, we used Fourier Transform to decompose the signal, and analyze the frequency spectrum. However, this method may only be suitable to stationary and nonlinear signal. Even though some researcher presented an alternative method called short-time Fourier Transform (STFT) to solve the disadvantage of Fourier Transform, we are not able to know the instantaneous frequency in the signal.
In order to solve the signal involved nonlinear and nonstationary property (earthquake), we used Hilbert-Huang Transform method to deal with it. This method was developed by Dr N, E. Huang in 1998. There are two advantages in this method. First, we don’t need to set the basic function. Second, we can identify the change of the instantaneous frequency. Through the Hilbert-Huang Transform, the signal can be expanded to the distribution of energy in time-frequency domain. We constructed two modal parameters (II,NI)in the time-frequency spectrum to quantify the physical behavior of the structure and use the parameters to monitor the health of the structure.
In this study, we used a finite element software; ABAQUS, to construct a five-floor structure model which has a local damage. Then, used the acceleration from the top of each floors as the original signal to draw the time spectrum. We selected the data from the spectrum and converted it into two modal parameters (II,NI) and a new parameter (DN) to compare the differences of each model. Moreover, to find the relation between the different models and apply this method to the real case of structure health monitoring. |
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