Research On The Center Of Gravity Threshold And Control Technology Of The Large Span Flat-Vertical Composite Rotating Arch Rib

Bridge turning construction technology can solve the problem of bridges in complex mountainous terrain conditions and has been widely used in recent years.The regulation of the center of gravity of the structure during the turning process is the key to determine the safety of the turning system,but because the structural system changes in real time during the vertical turning of the arch rib,it is difficult to make an accurate judgment of its center of gravity.In this thesis,the center of gravity threshold and regulation technology of flat-vertical composite rotating arch rib is studied based on actual engineering.The main research contents are as follows:(1)A continuous vertical rotation cable force calculation method is proposed,and the influence of pulley cable saddle friction is considered comprehensively.The cable force is precisely controlled by the cyclic iterative method.The results show that the calculated force is within 2% error of the measured force.(2)The contact algorithm is used to establish the fine-grained analysis model of the rotating ball hinge,and the relationship between the rotating moment and the node displacement is analyzed.Through the parametric analysis of the mechanical behavior of the rotating structure such as the spar foot and ball hinge,the calculation accuracy and efficiency of the complex rotating body model are improved.It is found that the local debonding of the contact surface of the spar foot has a significant effect on the stress of the spar foot,and it also has an impact on the force distribution of the spar foot and ball hinge.(3)In order to ensure the overturning stability of the rotating structure system,the overturning safety factor and the flat rotating traction force under unfavorable wind direction were calculated for various wind load conditions.The effects of wind speed,vertical turning angle of arch ribs and other factors on the turning process were studied.On this basis,the research on the center of gravity threshold of the turning structure was carried out.The expert evaluation system model and multi-factor evaluation model were adopted respectively,and the optimal center of gravity eccentricity distance of the turning structure was derived as 0.026 m and 0.025 m,respectively.(4)In order to grasp the position of the center of gravity in the dynamic turning process in real time,a real-time center of gravity monitoring and determination method for the turning process is proposed.By monitoring the deformation of key parts of the turning structure,the absolute center of gravity position and the offset distance of the center of gravity of the turning structure are inferred,and the dynamic center of gravity of the bridge is precisely located during the vertical turning process;the center of gravity identification system of the turning structure is developed with the visualization programming software Lab View.The system is successfully applied to the supporting project,providing a basis for the regulation and decision of the turning process of the supporting project.