The Dynamic Inverse Problems Of Bridge Subjected To Vehicle Excitation

Under the action of long-term vehicle load and natural environment,the bridge structure will inevitably be damaged.Therefore,the method of accurately identifying the bridge structure damage condition is of great significance for its safety assessment and maintenance.For the bridge health monitoring and evaluation under operational conditions,the damage identification method based on the vehicle-bridge coupling vibration response is more in line with the actual needs.Bridge structural damage identification belongs to the problem of system parameter identification.For bridge damage identification based on vehicle-bridge coupled vibration signals,it also involves the identification of vibration excitation sources such as unknown vehicle loads and road roughness.Therefore,aiming at the inverse of structural damage and vehicle-bridge interaction forces,two classical inverse problems,this paper conducted the following research by using the vehicle-bridge coupled vibration signals.(1)When the parameters of the moving vehicle are all known,this paper proposes an Extended Kalman Filter(EKF)based damage identification method,which is applicable to different types of bridge vibration signals(displacement,velocity and acceleration signals).In the case of smooth road surface,this paper analyzes the influence of measurement noise,damage degree,model error,moving speed and vehicle weight on the identification results.When considering the road roughness,in this paper,the bridge vibration response caused by road roughness is regarded as measurement error,and the influence of signal type and road surface status on identification results is discussed.(2)Due to the randomness of the road surface roughness,even if the vehicle parameters are all known,the vehicle-bridge interaction force can not be calculated accurately,which hinders the accurate identification of bridge structural damage.Therefore,in this paper,the vehicle-bridge coupling vibration problem is equivalent to the bridge vibration problem under the moving vehicle-bridge contact force.Then,based on the bridge vibration signal under the vehicle excitation,the EKF method is used to directly invert the time-varying vehicle-bridge contact force.The identification algorithm of the equivalent vehicle-bridge interaction forces is proposed,which provides a theoretical basis for the bridge structures damage identification with the condition of unknown road surface and unknown vehicle parameters.(3)Based on the above two research,this paper proposes two methods for common identification of vehicle-bridge contact force and bridge structure damage,namely,the vehicle-bridge contact force and structural damage step-by-step identification algorithm and synchronization identification algorithm.In the step-by-step identification algorithm,firstly,the bridge structure is assumed to be undamaged.Secondly,the vehicle-bridge contact force is identified under the undamaged bridge model.And then the vehicle-bridge contact force identification result is applied to the bridge structure for damage identification,next,the bridge model is updated by the damage identification result to identify the vehicle-bridge contact force once more.Finally,the vehicle-bridge contact force and the damage status of bridge structure can be obtained by repeating the identification process.Compared with the step-by-step identification algorithm,the synchronous identification algorithm still adopts the idea of iteration,but the vehicle-bridge contact force and the bridge damage condition are updated in the same Kalman filter recursive process.When the road condition is unknown and the vehicle parameters are unknown(the vehicle weight is known),both of the vehicle-bridge contact force and structural damage condition are accurately identified.