Damage Identification Of Continuous Beam Bridge Based On Statistical Characteristics Of Vehicle-Bridge Coupling Vibration Response

Most of the traditional dynamic damage identification methods need to interrupt the traffic and affect the normal operation of the bridge structure.At the same time,the damage identification effect is extremely dependent on the accuracy of the signal.Under the interference of road unevenness or test noise,the damage identification accuracy is not high.This paper aims to propose a damage identification method based on vehiclebridge coupled vibration displacement response,and construct a damage identification index that is sensitive to structural damage and has good noise robustness.In view of the fact that most of the current research focuses on simply supported beam bridges,this paper takes a three-span continuous beam as the research object,and analyzes the applicability of the damage identification method.The main research results are as follows:(1)The 1/4 vehicle model is used to simulate the driving vehicle and the modal coordinate method is used to establish the vehicle-bridge coupling vibration equations.The shortcomings of the mode shape function fitting method in the damage identification research are analyzed.Base on this,a new method for calculating the coupling vibration of vehicle-bridge is proposed.According to the characteristic of the fixed time step of the step-by-step integration method,the mode shape function in the equation equation is replaced by the mode shape vector,and the generalized parameters of the coupling equation are calculated by means of high-precision numerical integration.Finally,the Runge-Kutta method is used to solve the equation system,which is applicable to any speed cases.The numerical simulation results show that the method has the same calculation accuracy as the traditional mode shape function method,and at the same time greatly simplifies the calculation steps and reduces the calculation amount.(2)Through theoretical derivation,it is found that the dynamic response variance has good anti-noise performance.The damage index DSDC(Displacement standard deviation curvature)is constructed by combining the wavelet transform with it,and its applicability under complex damage cases is analyzed by numerical simulation.The results show that under the single-damage case,even in the case of minor damage to the bridge structure,the index can accurately identify the location of the damage,and the damage index can reflect the degree of damage.In the single-span multi-damage case,the interaction between different damage degrees is analyzed.When a large damage occurs in the middle of the span and a small damage occurs in the adjacent position,it may lead to the missed judgment of the small damage.And the damage identification effect in each span is different,which overall trend is the third span better than the second span and greater than the first span.In the process of multi-span and multi-damage numerical simulation,no damage was missed,and the DSDC index showed excellent damage identification ability.(3)The pavement roughness and noise sensitivity of DSDC index were analyzed,and it was found that under A,B,and C grade road cases,the index had stable damage identification ability;under the case of small damage,DSDC index only had a certain anti-noise performance and when the signal-to-noise ratio is lower than 26 d B,the damage information will be annihilated.When the structural damage degree is greater than or equal to 10%,the damage index proposed in this paper has strong noise robustness,and can accurately identify the damage position of the three-span continuous beam when the noise intensity is 5%.