Bridge Structure Damage Identification Research Based On The Dynamic Testing And The Research Of Bridge Comprehensive Evaluation Theory

Bridge is one of the important compositions of the transportation system, and the healthy situation of the bridge structure is the basis for the well operating of the transportation system. During the service lives of the bridge structure, affected by the loads, environmental collisions and natural disaster, the damages of the bridge are unavoidable. Once the damages amount to some extent, the structure of the bridge will be destroyed, which will cause damages to the state economics and the people's lives and properties. Therefore, it is of theoretical significance and practical value to make researches on the health monitoring of the bridge structure.Structural damage identification method is the basis and important part of the health monitoring of the bridge structure. In recent years, researchers tried a lot to find the damage identification method for the bridge structure. Structural damage identification method based on the dynamic test is the hot issue at home and abroad. Although the research of this method has made great progress and many damage identification methods and theories have been proposed, limited by the factors such as our understanding, the testing technique and the field condition, the structural damage identification method based on the dynamic test has not made any substantial progresses, and could not be in widely applied. Thus, to make research on the structural damage identification method which is proper in practice with accurate results is of great practical value. The thesis is based on the past studies and makes researches on the structural damage identification method aimed at the existed problems at present, and the contents are shown below:1 .Based on the comparison analysis of the existing sensor placement optimization, the improved sensor placement optimization method based on the energy coefficient-effective independence method was proposed, which compensated the weaknesses of the traditional methods. Reflecting the coefficient of the node freedom modal strain energy, the proposed method can modify the effective independence reflecting the maximum linear independence, and further optimize the sensor placement designs. Taking the simply supported steel truss beam bridge as a numerical example, the results showed that the evaluations of the designs were good, and the method can ensure the orthogonality of the measurement vibration pattern vector, and can also ensure the accuracy of the expanded order vibration and has better anti-noise ability, which is an ideal method appropriate for the bridge structure.2.Based on the traditional modal parameter structural damage identification, a damage identification index based on the grey relation curvature absolute difference was proposed. This index had high sensitivity to the structural damage and had good effects only in the need of the low-order modal information. Meanwhile, on the basis of the grey relation curvature absolute difference, the thesis suggested hierarchical identification method and multi-sample average dealing method to solve the incomplete of the measurement modal and the data noise. The numerical example illustrated that the proposed damage index could well reflect the structural damage and had better anti-noise ability.3.On the basis of the reverse problem and model modification method, the coordinate modal assurance criterion and the frequency were used to establish the optimization object function, and the damage identification method based on clonal selection algorithm was proposed, which overcomes the difficulty that during the traditional algorithm when the gradient matrix was morbid or singular, and the calculation would not complete. The calculation efficiency was improved by the proposed method. The identification damage in the simply supported steel truss beam bridge was also studied and the result showed that the proposed method could identify the location and the extent of the damage, had better ability of anti-noise, and was especially proper for the engineering practices.4.Multi-grade damage identification method based on the integrated neural networks was proposed, and the alerting, locating and extent identification were realized by step, which strengthened the generalization ability of the networks, made the networks scale smaller and reduced the training sample size and training time of the networks. The numerical simulation demonstrates that the proposed method is effective and has the anti-noise ability.5.On the basis of the completion and dynamic load test of Jin Shui Gou Bridge, the health condition was established. Relying on the subject of Jin Shui Gou Bridge health monitoring of China Academy of Railway Science, and according to the characteristics of the bridge, the health monitoring implementation design of rigid frame-continuous beam structure was made. Three methods which were proposed in this paper were compared through the research on the damage identification of main beam of Jin Shui Gou Bridge.6.0n the basis of the introduction of the traditional bridge comprehensive evaluation methods, the extension theory was applied in the engineering. The interval extension evaluation theory based on the combined weight was proposed and the bridge condition grade evaluation model was also established. The engineering case shows that the proposed model can make objective and reliable evaluations.