Optimization Of Flutter Measures And Stability Analysis Of Construction Stage Of Long-span Steel Truss Suspension Bridge

With the development of the western region,more and more large-span steel truss suspension bridges have emerged,and the steel truss with a combined deck plate is more favored by the designer and builder due to its light weight and high stiffness.The suspension bridge has a high flutter test wind speed in the mountainous area,and its flutter performance must be considered.In addition,with the increase of the span of the bridge,the construction period is correspondingly extended,and the flutter stability of the construction stage has received more and more attention,but the current research on the flutter performance of the steel truss suspension bridge in the construction stage is not sufficient.In view of the above problems,this paper mainly carries out the following aspects of work:（1）Aiming at the problem of flutter derivative recognition of bridge,based on the principle of least squares method,the flutter derivative recognition programs of the overall least squares method,the modified least squares method and the weighted least squares method are written,and the accuracy of programs are fully verified,and the applicability of the three methods is evaluated.The results show that the flutter derivative recognition results are more consistent for the overall least squares method and the modified least squares method.For the weighted least squares method,the time-course weighted matrix has a significant impact on the three flutter derivatives ofH₂^*,H₄^*and ₄A^*when the amplitude of the system time-course curve varies greatly.According to the trend of the flutter derivative,the overall least squares method and the modified least squares method are better than the weighted least squares method.（2）Through the wind tunnel test of the bridge’s section model,the flutterperformance of the steel truss suspension bridge with a combined deck plate were optimized,and the influence of various forms of stable plates and auxiliary facilities on flutter performance was studied,the accuracy of the results was verified by the full bridge reduce-scale model test.The results show that various forms of lower stabilizer plates have little influence on the flutter performance of the steel truss with a combined deck plate;only a high enough upper central stability plate can increase its flutter critical wind speed;and the inward movement of the railing can play a role similar to the horizontal stabilization plate.The research idea of aerodynamic optimization in this paper can provide a reference for similar bridges.（3）Through the full bridge reduce-scale model test and the three-dimensional flutter domain analysis method,the influence of beam segment connection methods and flexible central buckles on flutter performance during construction was explored.The results show that the use of different beam segment connection methods will have an impact on its flutter control mode shape,flexible central buckles only improve the flutter stability of suspension bridges when the flutter is controlled by anti-symmetry torsion;the permanent connection method has better flutter performance than the articulation method,and considering the wind safety and stress concentration of the steel truss,it is more reasonable that the suspension bridges adopt the articulation method in the early stage of construction,and then convert it into permanent connection according to the change of suspension bridge linear shape.