Study On The Construction Technology Of Two-Way Rotation Of A Small Radius Curved Groove Beam Across The Existing Line

With the leapfrog development of railway construction in China in the past decade,the intersection of newly built railways with structures such as railways,highways,and oil and gas pipelines has become increasingly common.Due to geological,topographical conditions,and the need for railway construction cycles,it is inevitable for new railways to cross existing operating railway lines with small radius curves and low headroom.The Wuhan Hub Hanxi Super Large Bridge spans the existing Handan Line and the existing Jingguang Line.The bridge type scheme first adopts a(37+64+37)m plate rib continuous channel beam structure,which adds a rib plate on both sides of the conventional plate web plate.The plate web plate is combined with the reinforcing ribs on both sides to jointly resist transverse and torsional deformation.At the same time,this structure is the largest railway concrete channel beam structure with the largest span at present,It is also the first time to adopt a groove beam structure with swivel construction.Through finite element model analysis,it is known that the stress,strength,and deformation indicators of the(37+64+37)m continuous channel beam structure of the Hanxi Grand Bridge meet the requirements of the specifications during the construction stage and operating conditions;Analyzed and studied the changing trends of the mechanical characteristics of the inner and outer sides of the web plate of continuous channel beam structures under different radius curves,such as support reaction force,bending moment,torque,shear force,normal stress,shear stress,vertical deformation,and lateral deformation,as well as their adaptability to the regulations of curved beam bridges in domestic and foreign design specifications;Analyze and study the variation trends of web shear stress,transverse deformation,and other factors under different spacing and thickness of rib plates for the plate rib type groove beam structure,and obtain the effect and influence of rib plates on the overall and local stress of the groove beam structure.The channel beam structure is located on a small radius curve,and the lateral pre eccentricity value affects the lateral balance and pouring position of the beam during the bridge rotation process.The calculation and precise positioning of the pre eccentricity value are the key and difficult points of construction control.By analyzing and studying the pre eccentricity value of the swivel ball joint design,the center coordinate of the ball joint is determined.Based on the direction,angle,and spherical joint coordinates of the bridge rotation,the beam prefabrication coordinates after the spherical joint pre eccentricity setting were calculated.By accurately positioning the center of the spherical joint and the position of the beam prefabrication,the basic lateral balance before the bridge rotation and the precise positioning of the bridge position after the beam closure were achieved.By combining the construction method of trough shaped beams and controlling the elevation of the beam bottom formwork,the stress,strain monitoring,and line monitoring during the beam construction process are strengthened,achieving that the beam line and elevation deviation before rotation meets the requirements of the specifications.The monitoring and measurement scheme achieves real-time tracking of the beam posture during the rotation of small radius curved groove beams without high-level placement of mirror points and when the centerline measurement points are not unobstructed.A calculation program has been developed to reduce the difficulty of collecting measurement data,meet the automatic evaluation of data validity,save a lot of data analysis time,and monitor the beam posture more effectively,greatly reducing the workload of adjusting the beam posture.Through engineering practice,it has been verified that this measurement scheme can achieve high-quality measurement of the beam posture of small radius curve continuous groove beams,and the measurement data results and beam posture are safe and stable.