Study On Some Methods For Identification Of Structural System And Damage

In recent years, more and more structural health monitoring (SHM) system has been installed in the civil infrastructure structures such as bridges, long-span space structures and ocean platforms. However, as one of the key techniques, the system identification (SI) and damage identification (DI) has never been ultimately resolved. It confines the function of the SHM system. Therefore, the further research of modal parameter identification (MPI) and DI method adapting the need of on-line SHM system has the important theoretical significance and engineering practical value. In this dissertation, some new signal processing technique such as Hilbert-Huang transform (HHT), Wavelet transform (WT) and computational intelligence technique such as genetic algorithm (GA) have been incorporated into the SI and DI problem of civil engineering structures. Some existing problems of applying these techniques to the SI and DI problem of civil engineering structures have been studied and some effective means have been proposed. The main contents are listed as follow:1. Based on the introduction of the research state of SHM system, as one of the key techniques of SHM system, the structural SI and DI problem has been highlighted and need to be studied further. Then, the research of the traditional and ambient excitation MPI methods and the research of the vibration-based DI methods have been introduced. Specially, the research of MPI and DI based on the HHT and WT has been reviewed in detail. At last, the main research contents in this thesis have been outlined.2. The rationale and some problem of HHT have been studied and the HHT has been used to identify the damage of stiffness abruptly and gradually of the SDOF structure, the damage time and extent has been identified.3. Through the numerical simulation analysis of the orthogonality of intrinsic mode function (IMF) decomposed by the empirical mode decomposition (EMD), the problem that the IMFs are not orthogonal has been putted forward firstly. Then, the orthogonal EMD (OEMD) has been proposed to resolve the problem and the complete orthogonal IMF that satisfying the requirement of IMF has been attained. The analysis of numerical examples verified the correctness and effectiveness of the OEMD. The OEMD has been used to analyze the earthquake recordings and the comparison between the Hilbert spectrum, the Hilbert marginal spectrum and the orthogonal Hilbert spectrum, the orthogonal Hilbert marginal spectrum shows that the latter can faithfully...