Study On Construction Control And Key Technologies Of V-braced Continuous Girder Bridge Of Long-span Railway

With the gradual improvement of China's high-speed railway network,when crossing rivers and existing lines,the prestressed concrete continuous beam bridge has been widely used because of its simple structure and reasonable stress.With the progress of bridge construction technology,the span of bridge is increasing constantly,which brings many uncertain factors to the construction process.In order to ensure the safety of the construction process,the linearity and internal force of the completed bridge meet the design requirements.It is necessary to carry out construction process control.Based on the background of Wenyuhe river Bridge of Beijing-Shenyang Passenger Dedicated Railway,this paper carries out construction control and key technology research.The main research contents are as follows:(1)The stress characteristics of V-braced continuous beam and the theory and method of construction control of continuous beam bridge are introduced.At the same time,aiming at special bridges such as V-braced bridge the key points and difficulties of construction control of such bridges are summarized.It lays a theoretical foundation for subsequent bridge structure analysis and construction process control.(2)Taking the Wenyuhe river Bridge of Beijing-Shenyang Passenger Dedicated Project as the engineering background,the structural finite element analysis models are established by using Midas Civil and Midas FEA respectively.The stress distribution law of main beam and V-brace structure during construction is studied.On this basis,the necessity of setting longitudinal prestressing tendons on V-braced base and the influence of the time of dismantling auxiliary piers on bridge structure are discussed.The necessity of prestressing tendons with V brace base is verified.At the same time,the removal of auxiliary piers after the completion of the bridge is more conducive to V-brace force and beam linearity.(3)Closure sequence is an important factor affecting the linearity and internal force of multi-span continuous beam bridges.Different closure sequence determines the difference between the main beam and V-brace linearity and internal force distribution.For the Wenyu River Bridge,four different closure sequence schemes are worked out,and the optimal closure scheme is determined from the aspects of structural stress,construction period and so on.It provides a reference for the selection of closure schemes of similar continuous beam bridges.(4)The construction of closure section is an important link in the construction process of cantilever casting continuous beam.The quality of concrete in closure section is closely related to the safety of bridge structure.When the construction method of closing section is adopted,in order to ensure the concrete quality of closing section,temporary locking of the rigid skeleton of closing section is usually needed.However,in order to meet the requirements of rapid construction of high-speed railway,the construction method of closure section without closure section of side span is more and more widely used.Under the action of temperature load,cracks may occur between the maximum cantilever end and the cast-in-place section due to inconsistent deformation.This paper puts forward the construction measures of applying support and counterweight at the cantilever end,which can effectively reduce the risk of cracks.(5)In the process of cantilever construction control of continuous beam,the control concept of linear control and stress control is applied.In order to guide the construction process and ensure the safety of the cantilever construction process,the elevation of main girder and stress data of key sections are collected and compared with the theoretical values.In the cantilever construction stage,the main beam linearity and internal force meet the design requirements,which laid a good foundation for the follow-up bridge closure.