| With the development of the national economy and the improvement of people’s living conditions,our country’s car ownership is increasing steadily.With the increase of vehicle load and traffic flow and the deterioration of the use environment,various types of bridges constructed in the early stage face the current situation of requiring reinforcement and replacement of components.The maintenance of bridges is usually carried out under closed traffic conditions,which will bring inconvenience to the travel of nearby residents,and also cause significant economic losses for bridges in urban centers or traffic trunk lines.How to complete the bridge maintenance project without interrupting traffic while ensuring structural safety and construction quality is an urgent problem to be solved.Therefore,relying on the cable replacement project of a large-span through concrete-filled steel tubular arch bridge and based on the measured traffic flow data of the Weigh-in-Motion(WIM)system,we have conducted research on the cable replacement process of tied arch bridges under uninterrupted traffic conditions in terms of vehicle load models,mechanical transmission mechanisms,and construction control.The main research contents and results are as follows:(1)Based on the measured data of WIM system,a vehicle load model suitable for the background bridge is established.Install a WIM system on the road of the bridge and continuously collect traffic flow data for one month,obtaining information such as the vehicle type,total vehicle weight,number of axles,axle weight,axle spacing,vehicle speed,and passing time of the vehicle crossing the bridge.Statistical analysis was conducted on the total weight of each vehicle type and the proportion of each axle weight to the total weight,adopt processes and methods similar to those for national specification development,establish a vehicle load model based on measured data.(2)Through the numerical simulation analysis of the background bridge,the mechanism of mechanical transmission during the replacement of cables for tied arch bridges is explored.Using the general spatial finite element analysis software,establish a three-dimensional finite element overall model of the background bridge and a temporary cable model.Using the temperature load method to simulate the tensioning process of temporary cables,the mechanical behavior of adjacent cables,main arch,and other components during construction is analyzed,and the mechanical transfer mechanism of the main load-bearing components is clarified.(3)A safe passage plan was proposed for the background bridge to replace the cable under uninterrupted traffic conditions.Based on the vehicle load model of the background bridge,the vehicle load parameters of four traffic schemes are established:normal traffic,limited traffic,semi-closed traffic and semi-closed limited traffic.Through finite element simulation analysis,the stress state of the main components of the bridge when the cable replacement under four traffic conditions are obtained,and their impact on structural safety and construction quality is explored,and the optimal traffic plan is determined.(4)Based on the research results of vehicle load model,mechanical transmission mechanism,safe passage scheme,etc.,the construction monitoring of cable replacement of background bridge under uninterrupted traffic conditions has been completed.The measured results show that the internal force,displacement and other indicators of the key sections of the bridge during the construction process meet the design expectations and relevant specifications.After cable replacement,the geometry of bridge deck is smooth,and the error between the finished cable force of each and the target cable force is within 5%.Relevant research results ensure the safety and quality of cable replacement construction of tied arch bridges under uninterrupted traffic conditions,and provide reference for similar bridge maintenance projects. |
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