Research On Construction Control And Key Technology Of Long-span Continuous Beam Arch Bridge Of High-speed Railway

Long span continuous beam arch bridge has the advantages of high strength,high stiffness,light weight,beautiful bridge type,strong spanning capacity and short construction period.It is often used as the preferred bridge type of long-span bridge in urban railway bridge construction.Taking a long-span continuous beam arch bridge as the engineering background,this paper discusses the construction control method,arch foot stress distribution,arch rib stability and the change of cross-section stress in the process of arch rib pouring(1)This paper summarizes the development status,structural form and stress characteristics of this kind of bridge,and puts forward corresponding construction control methods for the existing construction problems of this kind of bridge;Through the detailed division of the layout of stress deflection measuring points,the finite element model of the whole bridge is established,and the deflection and stress changes in each construction stage are calculated and analyzed.The results show that the bridge achieves the ideal control effect.(2)Through the direct model method,the solid finite element model is established to explore the stress distribution of the arch seat under different load conditions.The results show that the local tensile stress around the middle beam increases with the construction;The tensile stress of longitudinal bridge in the triangle area of arch foot increases gradually;When the arch rib just extends into the arch foot and the cross beam passes through the manhole,the stress concentration is easy to occur.In view of the stress concentration area,the feasible suggestions are put forward to prevent the arch foot concrete from cracking due to the excessive tensile stress.(3)The finite element method is used to solve the eigenvalues of the spatial bifurcation point instability of the arch.The results show that the stability coefficient of arch branch points decreases gradually,but does not exceed the requirements of the code,and the main instability feature is out of plane antisymmetric instability.Through the dual nonlinear finite element method,considering the material nonlinearity and geometric nonlinearity,the load displacement curve of the vault node is obtained.By comparing with the elastic load stability coefficient,it is found that the nonlinear effect on the stability analysis of the bridge is not significant,and its nonlinear effect can not be considered in the design and calculation.(4)The concrete pouring process of the arch rib abdominal cavity pumped to the top is adopted.Through the pouring analysis of the abdominal cavity without stiffening plate and the abdominal cavity with stiffening plate under different pump pressures,the response relationship between the web stress and displacement is obtained.The results show that the setting of stiffening plate is not that the more layers,the denser the spacing is,the better.It is suggested that the reasonable spacing of dumbbell shaped steel tube arch rib abdominal stiffening plate with 3M high arch rib section should be 65 cm.Under this size,the deformation of web plate can be well restrained,and the concentrated stress of web plate and upper and lower steel tube welding can be effectively shared.