Seismic Damage Identification Method Of Concrete Structure Based On HHT

Based on the new-emerging signal processing method, Hilbert-Huang Transformation (HHT), this paper focuses on the research and discussion of some problems of HHT and application of HHT in identification for linear structure modal parameters and seismic damage.In 1998, Doctor Huang of National Aeronautics and Space Administration (NASA) put forward Hilbert-Huang Transform (HHT), a new signal processing method. The main innovations embodied in this method are the present of the concept of the Intrinsic Mode Function (IMF) and introduction of the method of Empirical Mode Decomposition (EMD). Hilbert spectrum gives precise description of instantaneous frequency and amplitude, embodies higher presentation compared with Fourier spectrum and Wavelet spectrum. HHT has not been put forward for long time, so it contains some theoretical problems, such as envelop and mean curve fit, boundary effect, modes mix and so on. In order to deal with curve fit and boundary effect problems, this paper puts forward piecewise second parabola spline interpolation method and dummy sinusoid boundary prolongation method, and verifies their feasibility and superiority through simulation tests. Besides, this paper also gives one numerical example to verify the validity of EMD de-noising method.Once HHT was presented, it has quickly been used in many fields. At present, in the modal parameters identification field, some researchers have brought forward two methods, using HHT and RDT to identify modal parameters of linear structure and using HHT and NExT to identify modal parameters of linear structure. In the third chapter, this paper not only describes their basic principles but also summarize their virtues and flaws. In the forth chapter, this paper deals with the longitudinal strong motion records of Sheraton-Universal during the 1994 Northridge earthquake by using of the results researched in the forward, identifying time variant characteristics of the structure and modal frequency,damping ratio and mode shape of the structure after strong motion. In the fifth chapter, this paper calculates the first mode shape values of all floors through curve fit, and calculate the stiffness between stories of the structure according to special formula, and evaluate damage degree of every floor according to one seismic damage evaluation model. In order to verify of nicety of the identified parameters, this paper also calculates structural responses using the identified parameters through simplified structural model, and compares the...