Dynamic Load Identification For Radial Steel Gate In Hydraulic Structure

Radial steel gate is one kind of popular gate applied in hydraulic structures, and it's vibration problem is common in hydraulic projects. With the development of our country's hydraulic project, hydroelectricity and water transport construction, more and more high-head dams are built, the head fall of working gate, pothole size and brackets' length of radial gate are becoming bigger increasingly, and controlled size of gate become larger in low-head dam. A large number of gates need be opened partly, and working condition become more complicated day by day. So people pay more and more attention in flow-induced vibration, dynamic stability and safety reliability of gates affected by dynamic water pressure on gates.In order to diminish the vibration, it is not enough to improve hydraulic condition and optimize gate structure. Employing intelligent control method is further way to solve this problem. Moreover, it is very important to make online health detecting and damage diagnose. Ascertaining the load on engineering structure is the precondition of intelligent control, health detecting and damage diagnose. But it is quite difficult to determine the dynamic load on gate when the gate is vibrating, and the accuracy of measurement is very poor. So the dynamic load identification of radial steel gate is an important problem in hydraulic structure which should be settled imperatively.Dynamic load identification is the second kind of inverse problem in structural dynamics, which is utilized to attain dynamic driver according to the known dynamic properties of system and dynamic responses measured in actual situation. This thesis introduces several kinds of dynamic load identification in vibration structure, including frequent domain method, time domain method, wavelet orthogonal operator transformation method, time finite element method, method based on neural network and so on. Towards the major problems of these theories and methods, the author analyses them, compares with each other and makes a conclusion. Then the author discusses the issue about flow-induced vibration of radial gate. Proceeding from vibration types of gate, he analyses vibration properties and destruction cause. On the basis of these, he summarizes the major measures up till now and put forward intelligent control measure to diminish the vibration.After the author introduces Hilbert-Huang Transform which is a new signal analysis theory, he tests the stationarity of typical time domain data of stochastic fluctuant pressure making use of turn method and HHT method respectively. From that, he concludes that stochastic fluctuant pressure on radial gate can be treated asstationary random process going through all of states in the case of certain opening and the characteristic value can be obtained from random function theory and spectrum analysis.In this thesis, the simplified mechanics model is modified according to the principle making the structure's dynamic properties equal between the three-dimension finite element model and the simplified model, and the simplified three-dimension model of equivalent structure is created and the system parameters are determined. Making use of this simplified mechanics model, the time domain method of dynamic load identification is put to use on the basis of modal analysis method. And the simulation analysis about stochastic fluctuant load identification on radial steel gate manifests the feasibility and the effectiveness in hydraulic structure.