Research On Force Performance And Unbalanced Torque Analysis Of Rotating Structure Of Flat-turned Bridge

In recent years,with the continuous development of China’s transportation infrastructure construction,the number of cross-line bridge projects has increased rapidly,and the use of turning construction technology will minimize the impact on the normal operation of adjacent roads and bridges and other traffic lines,so it is widely used in actual construction,but the theoretical understanding of the turning process has always lagged behind practice.In this paper,the spatial simulation model of the rotating system is established with the engineering background of the Wu Da high speed upper span turning overpass.And the mechanical characteristics of the ball-hinged structure at rest and in the rotating state are analyzed and studied by combining theoretical analysis and finite element calculation,revealing the distribution law of the ball-hinged contact stress,the mechanism of force transfer under the bearing platform of the turning body and the force state of the pile foundation,the influence of the eccentric state on the rotating system is investigated,and the balance control of the turning body is proposed.The effect of eccentricity on the rotating system is investigated,and optimization suggestions are made for the balance control of the rotating body.The main work of this paper is as follows:(1)Based on the basic theory of ball-hinged contact stress,four theoretical methods of calculating ball-hinged contact stress were selected and compared with the measured stress and finite element calculation results,and it was found that the results of the canonical algorithm,half-plane body and half-space body subjected to uniform pressure algorithm all showed that the average stress of ball-hinged contact had small errors compared with the measured and simulated analysis values.(2)ABAQUS software was used for finite element modeling analysis to reveal the stress distribution law of the contact surface of the ball hinge at rest,and to investigate the influence of controlling the parameters such as spherical radius and plane radius of the ball hinge on the force state of the ball hinge structure.The nonlinear time analysis of the rotating system under different rotating angular velocities and angular accelerations is carried out,and the maximum permissible rotating speed and permissible angular acceleration for the rotating process to ensure the structure in a safe and stable state are found.The stress performance of the rotating lower bearing and lower pile foundation was also studied,and the effect on its stress state and displacement was analyzed by changing the thickness of the lower bearing and pile length.(3)Different beam eccentric distances are selected and the corresponding unbalanced torque values are applied to the finite element model for the analysis of the rotating system forces.It is found that the eccentricity distance has limited effect on the vertical stress of the ball hinge and the lower bearing pile foundation in the stationary state,and mainly affects the displacement of the edge of the ball hinge;while too large eccentricity of the beam will cause the rotating structure to be in an unfavorable state during the rotation process,which requires advance counterweight to balance.When the rotating structure is in the stage of faster rotation speed,the more significant the influence of beam eccentricity on it.(4)Based on the balance weighing test and combined with the calculation results of the maximum static friction factor after the actual engineering test rotation,the new calculation formula for the frictional moment was verified and the results of the new formula were found to be more consistent with the actual values;based on the ball hinge stress difference method,the regression coefficientλwas introduced to optimize the unbalance torque prediction calculation formula,and a more accurate stress measurement point location y_λwas derived,and the applicability of the new formula was verified by the actual weighing test result and other engineering examples.The applicability of the new formula is verified by the actual weighing test results and other engineering examples.