Linear Control And Analysis Of Main Cable And Steel Box Girder Of A Self-anchored Suspension Bridge

Suspension bridges are widely used in the construction of long-span bridges,because of their beautiful linearity and the rationality of structural forces.The steel box girder self-anchored suspension bridge not only has good mechanical performance,but also has strong spanning capacity.It has become the first choice to build bridges in urban inland rivers,as well as the landscape engineering of the city.The construction technology of self-anchored suspension bridge is complex.In order to achieve the ideal design alignment,the alignment control of self-anchored suspension bridge has become the focus of similar projects.Based on a self-anchored suspension bridge with steel box girder,this paper makes a thorough study on the alignment control of the main cable and steel box girder from the construction process to the use stage through theoretical analysis,finite element simulation and on-site alignment monitoring of the suspension bridge.The main research contents are as follows:(1)Based on the design parameters of self-anchored steel box girder suspension bridge,the finite element model is established.The stress-free length of main cable and suspender is determined by simulation calculation,which provides processing length for factory manufacturing.The theoretical alignment coordinates of empty cables are iterated by the upside-down-forward analysis method,and compared with the coordinates of design control points.By comparing theoretical empty cable with completed bridge alignment,the pre-deviation of saddle and anchorage point is determined,which provides necessary guidance for construction.(2)In order to ensure the safety and stability of the suspension bridge system transformation process,the proposed suspension pole tension scheme is analyzed.There are many tension steps in the scheme.Although the main girder deformation is small and the main cable shape is reasonable,the construction period is long.By optimizing the tension scheme and adopting the principle of double control of force and displacement,the tension step of the suspender is reduced and the construction period is reduced to half of the original one.The construction results show that the system transformation is carried out with this scheme,the anchor head exposure and the suspender force meet the requirements of the code,and the main cable and girder alignment meet the design requirements.(3)According to the linearity control scheme,the monitoring results are compared with the simulated linearity,and the reasons for the difference between the two are emphatically analyzed.By modifying the finite element model,a more realistic finite element model is determined.According to the monitoring results in the construction process,the linear variation law of main cable and steel box girder in each stage is analyzed,which provides the basis for the design and construction of suspension bridge.(4)After the completion of the construction of the suspension bridge,the load test of the completed suspension bridge is carried out,and the measured deflection and strain of the steel box girder of the completed suspension bridge are compared with the theoretical calculation value.The results show that the measured strain and deflection of the control section of the steel box girder of the suspension bridge are in good agreement with the theoretical calculation.The construction quality of the steel box girder is good,the working performance is excellent and the safety reserve is high.This analysis provides basic data for the health monitoring of the suspension bridge in the operation stage.Through this study,the linear construction control method of self-anchored steel box girder suspension bridge is improved,which provides a useful reference for the design and construction of similar projects.