Structural Damage Identification Method Based On Vehicle-Bridge Coupling Dynamic Response Analysis

The bridge inevitably encounters structural damage in the serving cycle for the longtime vehicle loads,harmful environmental factors and material aging.When the damage accumulates to a certain extent,it would lead to performance degradation,and even the collapse accident of the bridge.Therefore,it is particularly important to detect the structural hidden damages in bridge in early probable serving time.In this paper,based on a whole-process-iterative method,the vehicle-bridge coupled vibration analysis is respectively conducted in two-dimensional and three-dimensional vehiclebridge models.The DDI(Difference of displacement integral)and DSI(Difference of strain integral)indexes based on deflection and strain response time-history are presented to locate the damage.And the RID(Ratio of integral difference)index is built with DDI for the aim to quantify the damage.Diversified parameters analysis is carried out with a few of set damage cases to verify the identification capacity of DDI,DSI and RID.In addition,the presented indexes are also applied in a case study,in which a serving continuous rigid frame bridge is simulated in several damaged specimens with common web cracks.The main research work in this paper is as follows:(1)A two-dimensional vehicle-bridge coupling vibration system is solved by the separation iteration method,and the characteristics of difference with quasi-static deflection response are analyzed.Accordingly,components analytical discuss is conducted to the difference of deflection time-history.And a structural damage identification method is proposed using DDI index.Multi-parameter studies are carried out with damage level,driving speed,road roughness,multiple damage and whole bridge stiffness degradation.The performance of DDI is verified.(2)Based on a three-dimensional vehicle-bridge coupling vibration system,local damage cases in a simple supported box-girder are simulated.The damage identification effect of DDI and DSI index are discussed with different damage location,damage level,driving speed,road roughness,road degradation,driving lane and multiple damages.(3)A reinforced concrete continuous rigid frame bridge is modeled in finite elements.The numerical FE model and vehicle-bridge coupling vibration calculation method is verified according to the measured modal information and dynamic strain measurement.According to the very common crack disease in girder web and the connection segment of girder to pier column,several damage cases are simulated by stiffness degradation at local elements.Then identification effect of DDI and DSI indexes are obtained using the dynamic strain and deflection simulation measurement.The results show that conditions of whole bridge structural stiffness degradation,local damage(s)in transverse multi-girder or longitudinal multi-segment also can be identified with the presented method in this study.Some restrictions and disadvantages of the proposed indexes are also discussed.