Research On Mechanical Characteristics Of Rotation System Of Large Tonnage Rigid Frame Bridge

With the constant development of China's transportation infrastructure construction,highway and railway transportation are the core parts of the transportation network.The total mileage and road network density have increased year by year,and the number of bridges across the road has risen sharply.The use of the rotating construction method to construct cross-line bridges can effectively prevent the construction from affecting the normal operation of existing lines,and the construction of large-tonnage cross-bridges will be the trend of future bridge engineering development.The study of the structural condition of large-tonnage bridges during the rotation process will ensure the safe,steady and rapid development of bridges with rotating structures.This paper relies on a large-tonnage(80m+80m)T-type rigid-frame bridge with high-heavy-wide structure characteristics.The midas FEA is used to simulate the swivel process precisely.Analyze the stress state of the upper structural box girder concrete and the turntable platform concrete in the uniform rotation stage,and study the stress response of different accelerations of the rotational acceleration stage to the concrete of the turntable platform;According to the results of on-site weighing test,the longitudinal unbalanced loads and lateral unbalanced loads of the rotating structure were measured.In the uniform rotation phase,when the load is unbalanced,analysis of the stress conditions of the concrete of the upper structural box girder and the turntable platform.Based on the unbalanced load measured by the on-site weighing test,study on the stress response of the unbalanced load in the uniform rotation phase to the concrete of the upper structural box girder and the turntable platform.The rotating ball hinge is the core part of the rotating system.Analyze the stress state of the steel ball joint during the rotation of the rotating structure during the rotation process,and study the stress response of the rotating ball joint with different rotation angle acceleration in the acceleration rotation stage during the rotation process.Based on the unbalanced load measured by the on-site weighing test,study the effect of unbalanced load on the force effect of the steel ball hinge during the rotating stage.Research conclusions:(1)In the rotating phase of the rotating structure,the angular acceleration has no effect on the compression concrete of the turntable platform,and the angular acceleration is in a parabolic relationship with the tensile stress generated by the concrete in the tension state of the turntable platform.With the control of the concretetension of the turntable platform,the angular acceleration limit is 0.6rad/s2;The angular acceleration is in a parabolic relationship with the maximum shear stress of the ball joint,in order to control the shear failure of rotating ball joints as a control condition,the angular acceleration limit is 0.8rad/s2.Therefore,the rotational angular acceleration of the rotating structure should be controlled at 0.6rad/s2.(2)In the stage of uniform rotation of the rotating structure,the influence of unbalanced load on the tensioned concrete of the superstructure should be considered;The unbalanced load has no obvious influence on the concrete under pressure in the turntable platform,while it has significant influence on the tensile state of the turntable platform due to local pressure.When the swivel structure reaches four times the reference unbalanced load,the turntable platform is located in the region of local tension stress on the eccentric side and the concrete is in the yield state.Unbalanced load has a significant effect on the height difference of the outer ring of the rotating ball joint,when the swivel structure reaches four times the reference unbalanced load,the elevation difference of the ball joint outer ring does not meet the specified requirements;Unbalanced load has a significant effect on the stress of the rotating ball joint,when the swivel structure reaches five times the reference unbalanced load,the ball joint is in yield.Therefore,the allowable unbalanced load of the swivel structure is four times the reference unbalanced load(39790.0k N·m in the longitudinal direction and 11385.4k N·m in the lateral direction).