Research On Damage Identification Of Continuous Beam Bridge With Variable Cross-section Based On Vehicle-bridge Coupling Vibration Theory

During the operation of the bridge due to adverse factors such as vehicle load and environment,the bridge structure will inevitably suffer different degrees of damage.If left to its development,the structure will suddenly fail,causing huge economic losses and bad social impact.At present,most bridge damage detection methods need to interrupt the traffic and close the bridge.For some roads with very heavy traffic,it is often difficult to interrupt the traffic.Therefore,it is of great practical significance to carry out damage detection and health monitoring on the bridge structure without affecting the normal operation of the bridge.Based on the vehicle-bridge coupling vibration theory,this paper studies the damage identification of continuous beam bridges with variable cross-sections.The main research contents are as follows:(1)This paper introduces several classical calculation models of vehicle bridge coupling vibration and take the common 1/4 vehicle model as an example.After establishing the vehicle-bridge coupling vibration equation of the vehicle model and the bridge structure,the Runge-Kutta method was used to compile the corresponding numerical analysis program of highway bridge vehicle-bridge coupling vibration under the MATLAB environment.The dynamic response of the mid-span displacement of the bridge is obtained,which helps to carry out the damage identification research in this paper.(2)This paper analyzes the influence of three groups of parameters,including vehicle mass,vehicle speed and vehicle spring stiffness,on the damage identification of continuous beam bridge with variable cross-section.The results show that: when the vehicle mass is large,the bridge damage identification effect is good;lower driving speed is conducive to the bridge damage identification research;the influence of vehicle spring stiffness is very small,which can be ignored.(3)Based on vehicle-bridge coupling vibration response,a damage identification method of highway bridge is proposed.According to the phenomenon that the vibration mode function and natural frequency will change before and after the damage of bridge structure,the displacement time history dynamic response of the bridge in each span is obtained through the self-made vehicle bridge coupling vibration analysis program for comparative analysis.Taking a three span continuous beam bridge with variable crosssection as an example,several damage cases are analyzed.It is concluded that the distance between the location of the damage and the location of the measuring point is an important factor affecting the effect of damage identification.The closer the distance between the two,the better the recognition effect;the damage near the bearing is not easy to be identified,and errors may occur.The damage identification method in this paper has good applicability to single damage and multiple damages.