Damage Detection On The Girder Of Cable-stayed Bridge Based On Cable Force Response Excited By Vehicle

The cable-stayed bridge has been widely used in engineering for its advantages such as aesthetic appeal and spanning capacity. With the increase of service time, damage for cable-stayed bridge will be appeared because of the effect of environmental erosion, overloaded vehicle and so on,and those damage may affect the performance and safety of the bridge structure, even lead to irreparable economic losses. Therefore, it has a very important practical significance to make accurate recognition of the location and extent of the damage in early stages for cable-stayed bridges. In order to solve the problem of damage detection, a new damage detection method based on cable force response caused by moving vehicle-induced vibration is proposed in this thesis, the main research work is as follows:(1) Based on the vehicle-bridge coupling vibration theory, vibration equations of the bridge-vehicle coupled are established in damage status. Cable force responses caused by passing vehicle are analyzed by numerical method in different damage conditions.(2) According to the theory of sensitivity analysis, a new damage identification method combined the cable force response caused by moving vehicle-induced vibration with sensitivity method is proposed for the girder of cable-stayed bridge. The stiffness reduction of the main girder element for cable-stayed bridge is defined as damage factor. The sensitivity matrix which is the cable force response for main girder’s damage factor is built by the finite difference method. And then, the sensitivity equation which is established by the sensitivity matrix is solved by Tikhonov regularization method. The damage factors are obtained by sensitivity equation to detect the damage of cable-stayed bridge. Finally, taking the test model of a single–tower cable-stayed bridge in laboratory for example, numerical simulation with single damage and multi-damage is studied and the results show that the presented method is correct and creditable.(3) The effect of damage detection for the various parameters in this method is discussed, such as different ?α, different cables, vehicle load parameters and noise. It is shown that the random cable force response of the cable stayed-bridge can be used to detect the main girder’s damage and the presented method has wide prospects for engineering applications. It is also shown that the method is insensitive to the vehicle’s speed and vehicle parameters such as mass, suspension stiffness and it has strong applicability and the influence of the noise to the identification effect is great, so the accuracy of the damage detection can be ensured by improving the measuring precision.