Study On Damage Identification Of Bridge Structure Based On Multi-Point Dynamic Deflection

With the development of testing technology,dynamic deflection,as an important index to describe the overall deformation of bridge structure,is becoming more and more convenient and accurate.The research on bridge damage detection based on dynamic deflection has been paid more and more attention.However,there are few studies on model damage identification based on sensitivity analysis.Based on this,this paper makes a series of research on the damage identification method of bridge structure based on the sensitivity analysis of dynamic deflection response using a few measuring points of the bridge under vehicle load as the modified target.The main contents of the thesis are as follows:(1)The dynamic response equation of the vehicle-bridge coupling system is derived based on the interaction between the vehicle model and the bridge structure.The main dynamic characteristics of the structure are obtained by modal analysis.(2)A damage identification method based on sensitivity analysis of dynamic deflection response of bridge is established by using dynamic deflection of bridge under vehicle load.The effectiveness of the algorithm is verified by setting different damage conditions for vehicle-bridge coupling system.The results show that structural damage and model error can be accurately identified by using single point dynamic deflection of any measuring point under noiseless condition,but the recognition accuracy of the algorithm is greatly affected by the test noise.At the same time,the influence of test noise can be reduced by using multi-point dynamic deflection.(3)Based on the method,the influence of the wavel et component is selected and the influence on the recognition accuracy.The results show that the low frequency component sensitivity can improve the recognition accuracy of the algorithm while reducing the compu tation of the algorithm,but the damage misjudgment is still prone.(4)Based on dynamic flexible wavel et sensitivity recognition method,a structural damage recognition method based on probability reliability theory is proposed and verifies the validity of the vehicle-bridge coupling system.The research results show that the damage quantification and positioning of the damage degree index based on multiple recognition results of test data can effectively reduce the impact of measurement noise;the two types of damage probability indicators have good convergence with the increase of test data groups,and high recognition accuracy can be achieved under the condition of limited group test data.