Study On Health Monitoring And Safety Evaluation Of Concrete-filled Steel Tubular Arch Bridge

In the long-term operation of the bridge structure,the bridge destruction accidents caused by concrete creep,damage accumulation,steel bar corrosion and slippage of the anchor end of suspender have occurred constantly.Good bridge health monitoring can grasp the working status of the bridge in real time and escort the safe operation of the bridge.Therefore,the bridge health monitoring system has been implemented in many bridges.A high-performance bridge health monitoring system must have the accurate acquisition of bridge state characteristic parameters,rapid and accurate data processing,and rapid and accurate evaluation of the bridge operation condition.However,due to the intricately intertwined multiple factors such as the bridge structure itself,load,and environment It is difficult for the existing bridge health monitoring system to fully consider the complex effects of multiple factors to accurately and quickly evaluate the safety of the bridge,and its monitoring and early warning functions need to be further studied and improved.This paper takes the health monitoring of the Xihu bridge as the research background,combined with real-time online monitoring and regular inspection to conduct health monitoring and safety assessment of the three-span continuous concrete-filled steel tubular arch bridge.The online monitoring system includes the extraction of bridge characteristic parameters,data processing,and analysis,and the design of early warning values,which are combined with the regular inspection of the suspender cable force to comprehensively evaluate the safety status of the bridge.The main research contents include:（1）A finite element calculation model was established based on the actual structure of the Xihu Bridge.According to the load-bearing capacity and deformation of the bridge,the sensors were optimized and the characteristic parameters of the bridge operation state were obtained in real-time,including deflection,strain,crack width,bridge end displacement,and temperature.（2）Preprocess the data in the online structural monitoring system to eliminate measurement errors.Eliminate the influence of temperature through the difference method and convolution filter method.And set the warning value based on the ultimate bearing capacity of the bridge.（3）Adopt the method of regular inspection to collect the relationship between the acceleration of the bridge deck,the strain of the suspender and the traffic flow on the bridge,obtain the law of the acceleration of the bridge deck and the strain of the suspender by the heavy vehicle,study the influence of the action of the heavy vehicle on the bridge,and combine the limit of the bridge Carrying capacity,perfect the setting of early warning value.（4）A multi-parameter joint early-warning mechanism has been established to solve the shortcomings of single-value early-warning being easily disturbed in online monitoring.（5）The frequency change of the suspender is regularly monitored.The calculation formulas for the amount of suspender slip and the change of natural frequency are put forward.Combined with the suspender boom slip and online monitoring data to make a comprehensive assessment of the health of the bridge（6）In view of the large error in calculating the cable force of the short suspender using the frequency method,a formula for calculating the cable force of Suspender.The accuracy of the method is verified through experiments.