The Research Of Flutter Instability Of Long-span And Slender Suspension Bridge With A Steel Truss Stiffened Girder

With the development of the western region,suspension bridge with steel truss stiffened girder is reaching the building climax. That's because its particular advantages in the western region. But the stiffness and damping of such suspension bridge are small,which make the flutter critical wind speed relatively lower. So the problem of flutter instability is the key for the wind-resistant design of the bridge. For the lack of research on the aerodynamic stability of long-span and slender suspension bridge,the wind resistant design for this kind of bridge is especially indispensable.First of all,the existing flutter analysis theory and a detailed introduction of the full-mode flutter analysis are present. As engineering background, the Xin jiang Sai wudiege'er bridge is a steel truss stiffened girder suspension bridge with 278m main span and 4m wide deck. By wind-tunnel test of sectional model and full-mode flutter analysis realized in ANSYS, flutter instability of the bridge was studied. The results show that: long-span and slender suspension bridge leads to flutter instability in the low-wind speed; The flutter critical wind speed obtained from "Wind-resisent design specification for highway bridge", ("Wind-resisent specification"for short)formula is lower than from wind-tunnel test of sectional model; Due to the impact of railings which is relatively higher than truss girder, the flutter critical wind speed is lower under negative angle of attack than under the positive angle of attack. Because the original design can't meet the"Wind-resisent specification", so the appropriate wind-resistant measures should be increased to improving the flutter critical wind speed.On the basis of introducing various wind-resistant measures to improve the suspension bridge flutter critical wind speed, the wind-resistant design is studied for the long-span and slender suspension bridge. After the structure wind-resistant measures were taken to optimize, the comprehensive wind-resistant measure was determined. The wind-tunnel test of sectional model and full-mode flutter analysis show that the bridge flutter instability has been greatly improved after increasing the comprehensive wind-resistant measure. The wind-resistant measures, such as wind-resistant cable, the central buckle, railings participating in the stiffness of the structure, could significantly increase the stiffness of girder and raise torsional fundamental frequency of the bridge. So that can be used as effective Methods to improve the flutter critical wind speed of the long-span and slender suspension bridge.