Study On Rotation Safety Performance Of Long-Span Box Girder Bridge Considering Slideway Irregularity

The bridge swivel construction technology is widely used in the construction of overpass bridges because of its convenient construction,safety and reliability,and small influence range.As a key component of the bridge swivel structure,the slideway is the cornerstone and channel of the bridge swivel.Due to the influence of uncontrollable factors such as production,transportation,assembly and construction environment,it is easy to cause large irregularities in the slideway,which in turn affects the safety and stability of the bridge swivel.Therefore,it is very important to research on the safety performance of large-span box girder rotation under the condition of slideway irregularity.This thesis takes a 2×60 m long-span box girder swivel bridge as the research background.By means of real bridge monitoring and test,refined numerical analysis and other research methods,the influence of slideway irregularity on the stress,deformation,vibration and other safety performance parameters of the key parts of the long-span box girder swivel bridge is studied.The main work and research contents of this thesis include the following four parts:（1）Based on the finite element numerical analysis and on-site real bridge monitoring,the experimental study on the safety and stability of bridge swivel caused by slideway irregularity is carried out.The research shows that the safety performance parameters obtained by field measurement meet the requirements of the specification,and the measured results of each safety performance parameter are consistent with the numerical simulation results,which effectively verifies the rationality of the safety monitoring system for the swivel construction of long-span wide box girder.The beam end tremor caused by the irregularity of the slideway occurs during the rotation process.（2）The influence of slideway irregularity on the dynamic performance of swivel bridge is studied by means of real bridge monitoring test and numerical simulation.The research shows that there is a large irregularity in the measured slideway,which has a great influence on the vibration of the beam end during the rotation of the long-span box girder.The change rate of the irregularity difference of the slideway is proportional to the vibration response of the beam end of the rotating box girder.The greater the change rate,the more severe the vibration of the beam end.With the gradual increase of the value of the slideway irregularity,the main beam alignment,the stress of the supporting foot,the vertical acceleration and the dynamic deflection of the beam end increase,and the influence on the safety of the dynamic performance of the bridge also gradually increased.（3）Based on the analysis method of slideway irregularity difference,the theory of rigid body fixed axis rotation and the simulation analysis of improving the horizontal rotation speed,the influence of different rotation stages and different horizontal rotation speeds on the safety performance parameters of the main structure of the bridge is studied.The results show that the angular acceleration of single point support increases with the increase of traction force,while the angular acceleration of multi-point support is related to the size of traction force and foot contact area.The stress values of the main girder and the pier bottom gradually increase with the increase of the rotational speed in the starting acceleration stage.When the speed exceeds 0.04 rad·min^-1,the torque is too large and the stress at the pier bottom exceeds the specification requirements.In the uniform rotation stage,increasing the rotational speed only has a small effect on the stress at the pier bottom.The irregularity and rotational speed of the slideway are the key factors affecting the dynamic response of the beam end during the rotation process,which should be controlled in practical engineering.（4）Based on the theoretical analysis results,the latest scientific research results,the design specifications of highway bridges and the related theories of bridge rotation,the research on the safety performance evaluation standard of long-span box girder rotation is carried out.The research shows that the safety performance evaluation method of long-span box girder rotation can effectively solve the safety performance evaluation problem of the structure in bridge rotation,and the relevant safety performance parameters of the background project in this thesis meet the requirements of the recommended evaluation standard,which effectively verifies the applicability of the recommended standard for safety performance evaluation of long-span box girder rotation,and can provide reference for similar projects.