Modal Parameters Identification Of Bridge Structure Based On Hilbert-huang Transform

The modal parameters identification of structure is the foundation and premise of several studies and application fields, such as structure health monitoring, damage detection, dynamical character analysis,etc. However, traditional modal parameters identification method is confined to the time domain study or the frequency domain study,and there are many disadvantages existed in traditional methods. Fortunately. Hilbert-Huang Transform (HHT) is a kind of modern time-frequency analysis method which can deal with non-linear, non-stationary signals, therefore, it has a great potential in aspect of modal parameters identification with structure. For those purposes, this thesis will concentrate on the study of bridge structure based on the theory of HHT, and the following works have been done:Firstly, advances in structure modal parameters identification is introduced in detail, and HHT as a time-frequency analysis method is adopted to settle the problem of modal parameters identification. What’s more, the basic theory and basic algorithms of HHT method is also illustrated in this thesis.Secondly, the HHT algorithm is realized through program, the efficiency of the algorithm is validated by examples that employed to work out the problem with specific technical support.Thirdly, with the end effects existed in HHT method, a new method is put forward based on mirror extension and support vector regression machine in order to control the end effects, through a simulation example, it is showed that the new method has the characteristic of extremely adaptability, and is worth of being generalized widely.Fourthly, the newly improved HHT method is applied to a three degrees of freedom system and a simply supported bridge. With the good recognition results of modal parameters identification, it is proved that the HHT method is effective and efficient.Fifthly, on the basis of effectiveness of the simulation examples, the newly improved HHT method is applied to model testing with a cable-suspension combined bridge, the results is identified effectively. As a result, the proposed method can be applied to practical engineering.