Research On Construction Monitoring Of Low Tower Cable-Stayed Bridges For High-Speed Railroads

Low tower cable-stayed bridge is a special form of cable-stayed bridge with the advantages of easy construction and high adaptability to the environment,which is widely used in the construction of high-speed railroad bridges.However,its construction process is more complicated than that of general continuous girder bridges,and reasonable construction control is required to ensure the safety,reliability and economy of low tower cable-stayed bridges in complex construction.The core content of the construction control of low tower cable-stayed bridge is divided into three aspects--line control,stress control and cable force control.Line control refers to the prediction and correction of deflection changes during the construction of the main girder;stress control refers to the monitoring of the stress level of the most unfavorable section of the main girder;and cable force control refers to the monitoring of the cable tension and the provision of the subsequent cable force adjustmentIn this thesis,the construction control and parameter identification of the low tower cable-stayed bridge are studied with the new Hangzhou-Quzhou Railway Xin’anjiang Special Bridge as the engineering background.Firstly,the construction control theory and development history of the low tower cable-stayed bridge are introduced;secondly,the design drawings are used to simulate and analyze the Xin’anjiang Special Bridge,and the ideal structural deflection,stress and cable force of the design are obtained by iterative method of positive loading;after that,the sensitivity analysis of the bridge design parameters identifies that the main influencing parameters of the low tower cable-stayed bridge are self-weight,main beam stiffness,initial tension of the cable and local temperature The secondary parameters are the tensile stiffness of the cable-stayed cable,the system temperature effect and the creep parameter.Based on this,the Kalman filter and least squares algorithms were proposed for different ranges of application and accuracy of parameter identification.The control results are as follows: the difference in elevation of the center span of the bridge is 4 mm,the change in stress during the construction phase does not exceed 20%,and the error of the cable force does not exceed ±2%after the completion of the bridge,and the overall construction control results meet the specification requirements.