Study On Nondestructive Testing Techniques For Hydraulic Structure Based On Vibration Theory

Nondestructive testing techniques of hydraulic structure based on vibration theory are founded. The systematic studies on these techniques are completed by theoretical analyses, numerical simulations, experiments and in-suit detection.The frame damage detection methods using curvature mode are studied by numerical simulation. The characteristics of curvature mode are compared with those of traditional displacement mode. Numerical simulation result shows that displacement mode shapes is less sensitive to structural damage than curvature mode shapes, and locating structural damage is more difficult. Curvature mode shape can indicate the presence of initial damage and its severity, and locate initial damage of a structure effectively. Curvature mode shape is also suitable for detection of multiple damage in a structure. The experimental result verifies further that strain mode and curvature mode are more suitable for detection of initial damage in the structure than displacement mode.A new structural damage detection method called local damage factor is investigated. The validity of this method has been verified by experiments. And the method has been used to detect the damage of real structure. This method can easily determine the presence, severity and location of structural damage. Experiment and in~suit detection all indicate that this method can test structural damage with little equipment, is a direct, fast and inexpensive method, and suitable for damage detection of a full-scale structure. The influence of structural nonlinear and systemic noise was considered, so that the accuracy of damage testing has been improved.A new simplified numerical analysis for dynamic characteristics of Yellow River dike' s leakproof wall is introduced. The leakproof wall isa classic hydraulic structure affecting by surroundings. The springs with equivalent stiffness are used to replace the affection of surrounding soil. The equivalent stiffness and structural border conditions are determined by in-suit testing. The conclusion of numerical simulation shows that nondestructive testing techniques based on vibration theory are effective to detect the quality of leakproof wall, and suitable for large-scale detection specially.The affection of sensor placement on structural parameters testing is studied by finite bandwidth white noise vibration experiment. The experimental result shows that optimal sensor placement can improve testing accuracy. The in-suit testing results of dynamic characteristics of a real structure verify that there is different testing accuracy using different excitation. Optimal testing system can improve accuracy of structural damage testing.