Analysis And Key Technology Research On The Whole Incremental Launching Construction Process Of Large-span Steel Box Arch Bridges Of High-speed Railway

The arch-beam association bridge has the advantages of both beam and arch and beautiful shape,which is used widely in bridge construction.At present,the arch-beam association bridge constructed by whole incremental launching is rarely used in railway.Based on the 112.5m simply supported steel box arch of a super large bridge of Jingxiong intercity railway,this paper focuses on the whole incremental launching process and key technologies.The main research contents are as follows:(1)Summarize the classification and characteristics of multi-point incremental launching construction technology.This paper focuses on the stepping multi-point incremental launching,including the stepping launching equipment,working principle,advantages and disadvantages.At the same time,this paper also describes the relevant content of the incremental launching construction control,including the significance,principle,necessity and construction control content of the incremental launching construction control.(2)Midas civil finite element software is used to simulate the construction stages of the 112.5m simple steel box arch bridge of a super large bridge on the newly-built Jingxiong intercity railway.The stress and deformation values of the main bridge structure and each component in each working condition of the whole incremental launching process are obtained,and the most unfavorable section position and corresponding launching distance are obtained.(3)Through the analysis of the connection part of the support,the settlement results show that the strength of the weld joint between the support and the arch rib is insufficient.It is proposed to reduce the tension of the connection part by installing and tensioning the suspender first.Through the forward installation iterative analysis,it is concluded that 150 kn is the best cable force,which is the target cable force to install and tension the suspender.This method has been applied in the construction site and achieved good results.(4)There are many construction procedures after launching to the bridge position.As a temporary structure,there is a large tension and compression stress.It is proposed to reduce the support tension by tensioning the suspender,and reduce the support pressure by relieving the temporary pier.The construction sequence of dismantling the support and tensioning the suspender is obtained.In this construction sequence,the steel pipe columns are removed under the condition of small stress,which reduces the construction risk greatly,and has little impact on the arch rib and main longitudinal beam,which can ensure the construction safety.(5)Carry out construction control on the whole launching process of the whole bridge and each process after the completion of the bridge,including temporary pier reaction and deformation.The accuracy of the model is verified by comparing the field measured value with the numerical solution.The frequency method is used to test and adjust the field cable force,and the deformation and cable force value of the bridge erecting machine under this special working condition are tested to further verify the numerical simulation results.