Study On Modal Parameters Identification Of Structures Based On Hilbert-Huang Transform

Modal Parameter identification of civil engineering struetures play an important role in research and application fields such as structural health monitoring, structural damage assessment. In recent years, extensive research and application has been done to develop the methods of time-frequency analysis based on vibration signal. Compared with traditional methods of signal analysis, HHT is a new technology for the analysis of signal. Being totally adaptive, and not subjcet to Heisenberg uncertainty principle, HHT has been proved to be ideal method for non-linear and non-stationary data. HHT has been widely used in many disciplines,including modal parameter identification,and produced good results. According to the consideration mentioned above,this thesis forcuses on the following aspcets of researeh:1.Value simulation and computation example were taken to study the characteristic of HHT method.Classical signals such as superposed signal, linear frequency-modulation (Chirp) signal, freedom weaken signal was computed and analyzed,which has shown that HHT method is effective to analysis non-linear and non-stationary data,and also there were some questions such as endpoint problems and modal mixing and so on.2.Theory of modal parameter identification based on HHT transformation was studied. A new method of modal parameter identification was proposed in the paper, which was based on HHT method to peak-frequency bandpass signal.And needed analysing and computing programs were generated based on MATLAB. At first, power spectrum obtained from Fourier transformation lay out the distribution of modal frequency of the pulse excitation response signal. And then, bandpass response signal containing peak frequency was obtained by bandpass filter. Finally, modal parameters was identificated through HHT method based on the bandpass response signal.The result demonstrated that the method proposed in this article successfully soluted the modal mixing problem.And the endpoint effection on modal parameters identification was rejected in HHT by means of removing endpoints of analyzed signal.3.Experiment modal analysis was studied on the reinforced concrete frame. Modal parameters of the structure,including natural frequency, damping ratio, and modal shape,was identifecated using the method provided in the paper based on palse excitation response signal,which can be gathered in experimental condition. identification results of natural frequency being identical with the calculated values,testify that method of the paper was reliable.