Analysis On Nonlinearity And Coupled Vibration Of Powerhouse Structure And Identification Of Modal Parameters

With the development of the society and economy, the waterpower, as a regenerated energy source, is increasingly regarded and rapidly developed. By the increase of the capacity and size of the hydro-generator units,the vibration problems of power house structure are catching people eyes, The dynamics problems are the focus, which the domestic and overseas scholars are studying on. Presently, the non-linear dynamics, the fluid-solid interaction, the anti-seism problem and the modal parameters identification method of power house structure should be improvement.Thus this paper studies on the solution of both the positive and negative problem extracted from the projects and the analysis of vibration detection. The principal achievements of this dissertation are as follows:⑴The conventional method for anti-seism study of power station structure is the linear analyses which bases on the response spectrum method. A new anti-seism analyzing method is proposed, which is using the non-linear method and the seism time series method to study the anti-seism problem of power station structure. With the complete process simulation method, it makes displacement field, deformation, stress, cracking field more precise than the conventional method, which can describe the real response of structure. Also, it can shows the time, position and quantity of cracks and weakness of structure with the method. The analysis is of high value on the anti-seism study based on the capability and the damaging estimation of large scale power house structure.⑵The paper combines FEM with acoustic theory with strong interaction method, finite element dynamic equations are built, which provides the basis for analyzing characteristics of power house structure. Vibration characteristics of power house structure at dam toe are calculated with the method and the comparison of characteristics of power house structure at dam toe and in river channel is done to describe the FSI features, and it makes a foundation for safe production and avoiding resonance.⑶The excitation sources of powerhouse structural vibration in hydropower station includes: hydrodynamic forces, mechanical forces and electromagnetic forces. The coupled dynamic action between powerhouse structure and generating units is strong. Because of the vibration system is distinctly non-linear and of dynamic characteristics, it is difficult for conventional methods to solve vibration response of power house induced by internal fluid, but nerve network technology based on test data can highly and non-linearly reflect integrated characteristics of study objectives, regardless of mathematical and mechanical model and various complicated condition. The vibration response of hydropower station can be predicted. The method is simple, effective and of high precision. It is used in health monitor and vibration control fields.⑷The mechanical forces, magnetic forces and current pulse have a big effect on the vibration of power house, it is very difficult to identify model parameters of the structure. To work out a correct solution to identify model parameters and improve the precision, a new method in time domain is proposed: RDT+ARMA method. The method is that it abstracts free-decay signal contents from the signal with random decrement method, when dynamic load released. Model parameters are identified with ARMA method from the signals. And then an important method on identifying mode parameters is proposed. The method (EMD+RDT+ARMA) is based on environmental excitation, which decomposes original signal, the free decay signals of IMFs are abstracted with RDT method, and then model parameters are identified with ARMA method. The methods are simple, effective and of high precision, it is specially fit for the first modes parameters of a powerhouse structure.⑸The vibration test of powerhouse structure is an important path for detecting structure safety. The test data and vibration response changes under various loads of Three Gorges Powerhouse structure are analyzed. The vibration controlling standard is introduced in this paper. The vibration situation of the structure is evaluated. Various dynamic loads are analyzed theoretically and the structure response is calculated under the loads, and the test data is compared with theoretical data. That gets some valuable contents.