Research On Inverse Problems Of Hydraulic Structure In Dynamics Based On Flow Discharge Excitation

With the mass construction of hydraulic structure with high-head and large discharge,and with the trend of light-duty discharge structures, the problem of flow-induced vibration will become prominent,and in serious conditions the structure may be damaged and even be invalidated. So, study on damage diagnosis and health monitoring of hydraulic structure based on vibration response by discharge flow has practical significance for discharge flow structures. Combined with engineering in this paper,the inverse problems of typical hydraulic structures under discharge flow are researched in the following three aspects:Firstly, study on working modal parameter identification of hydraulic structure under discharge flow. Aimed at the difficult problem of exciting the prototype to test, combined with the characteristic of ambient excitation, the modal parameter of structure is directly identified according to the dynamic response of structure under ambient excitation in the paper. (1) A method of order determination and ERA is proposed to identify modal parameters of structures under the working state,and the system order is determined by the increasement of singular entropy of eigenmatrix. It can be used to solve the problem of system eigenmatrix order determination, and to identify the modal order and reveal the characteristics. (2)Based on the SSI method, the process of"three step method"is put forward to make more precise identification. That is,firstly the increasement of singular entropy is used to determine the system order and make the borderline of order is clearer and more stable.Secondly, eliminating the false modal parameters by the improved stabilization diagram makes the outcomes more precise and credible.Thirdly, average the identified results of each order ,and get the more precise results. (3) A large-scale comprehensive prototype vibration tests to the hydroelastic model of Laxiwa arc dam, Spillway dam and Left guide wall of Three Gorges are carried out during the working state. And the modal parameter identification theory under discharge flow proposed in the paper is applied to the operational modal parameter identification of these large-scale hydraulic structures, and the operational behaviors of these hydraulic structures are evaluated.Secondly, study on the time domain identification of excitation source for high arch dam under discharge flow. How to identify the excitation sources inducing vibration of high dam is one of the concerned problems for water conservancy. While the hydraulic structure is evaluated,it is necessary to inverse analyse the characteristicof excitation source acting on the whole structure through some observed dynamic response datum. Based on wavelet theory and dynamics and stochastic vibration theory,a inverse analysis method to identify multi-excitation sources is put forward using wavelet orthogonal operator transformation in this paper.According to the characteristic of hydraulic structure,the key technical problems to identify the sources are discussed. Based on the hydroelastic model of Laxiwa arc dam,the equivalent loads are computed depending on some dynamic observed displacements,and then the comprehensive evaluation aimed at flow-induced vibration of the dam is done.This provides the basis for dynamic monitoring and damage diagnosis of arc dam.Thirdly, study on damage diagnosis of hydraulic structure under discharge flow. Aimed at the damage diagnosis of guide wall and radial gate under vibration response by discharge flow is blank in the world,the following study is carried out.(1) A method of damage diagnosis for guide wall based on vibration response by dischargeflow is put forward.This method can identify the whole safe state of structure timely and accurately comparing with the traditional method with long static observeddisplacement,and this method has particular advantages. Based on the vibration response of a guide wall under discharge flow,damage diagnosis is done and the frequency health monitoring index of the guide wall is put forward. (2)Based on the radial gate with double inclined arms of surface hole in the engineering of Xinzheng, a multilevel damage diagnosis method for radial gate is put forward. This method is a aggregation of vibration theory, neural networks and pattern identification,local test, and make the combined index as input data of RBF neural networks,and make the damaged locations and degree as output data. Study shows that the method has better function to denoise and precise identified results,and this provides a new way to online state testing and monitoring for radial gate.