Research On Dynamic And Aerostatic Response Of Self-anchored Suspension Bridge

Many self-anchored suspension bridges have been designed and constructed for their esthetic appearance, favorable adaptablily, economical performance and other notable advantages. Combined with key problems of Western Issues of Ministry of Communications (No: 200631882350) and Doctoral Discipline for New Teachers Fund of Ministry of Education (No: 20070141073), a self-anchored suspension bridge—Jinzhou Strait Bridge is taken as an example, the natural vibration characteristics, seismic response, aerostatic response and flutter stability of the bridge were researched. The main work and conclusions are as follows:(1) Natural vibration characteristics of Jinzhou Strait Bridge and the ground-anchored suspension bridge model, which has the same structural parameters as Jinzhou Strait Bridge, is calculated. Furthermore, the influence of natural vibration changed by varied structure parameters is also studied. The results show that the main girder vertical frequencies of self-anchored suspension bridge is lower than the ground-anchored suspension bridge, while the longitudinal drift frequency of the former exceedes the latter 38%. Their lateral and torsion frequency of main girder , horizontal frequency of main tower, cable vibration frequency is closer. The changes of dead loads,stiffening stiffness and tensile stiffness of the main cable on structural changes in the frequency is greater ,while the changes of stiffness of main tower and tensile stiffness on structural changes in the frequency is very small.(2) Seismic response analysis for Jinzhou Strait Bridge is completed with time history method. Traveling seismic excitations, pile-soil-structure interaction and vertical excitations are discussed. The results show the above-mentioned factors are more important, which can not be ignored.(3) A certain number of iterations under each wind speed are adopted to consider static wind load non-linear. The influence of some factorson deck displacements, pylon displacements, aerostatic divergence wind velocities and mode frequencies are comprehensively investigated, such as the pile foundation rigidity, cable segmentations. The foundation rigidity has a greater impact on the lateral displacement of the beam and tower. Among the total wind loads on structure, the contribution of cables exceeds 20%.The aerostatic divergence wind velocity and dis placements will be overestimated if the added attack angle of the deck is omitted. (4) In order to consider the uncertainty of structural parameters,taken Dalian Jinzhou Strait Bridge as an example,the static wind displacement effect at the mid-point of main span caused by randomness of material character and geometry dimension is studied in detail with Response Surface Method. The accuracy of parameter fitting is also discussed. The results show that the variation of material and geometric dimension have a greater impact on displacement of self-anchored suspension bridge under static wind.(5) Based on three-dimensional flutter analysis theory of bridge, three-dimensional flutter analysis is conducted by using ANSYS software. Many factors simultaneously such as the influences of static wind action, self-excitation force of cables and modes of cables can be considered simultaneously in flutter analysis. Effects of some factors such as the initial attack angle and the static wind action on flutter stability of self-anchored suspension bridge are specially studied. The results show that the flutter critical wind speed is different under various initial angle of attack and the lowest wind speed under angle of attack is 3 deg; the changes in vibration characteristics have little effect on the flutter stability by Considering static wind, while angle of attack of main beam has significant effects; self-excitation force of cables and modes of cables can improve flutter stability;Coupled aerodynamic derivatives A₁^* , H₃^* and non-coupled aerodynamic derivatives A₂^*, A₃^* have significant effect on flutter stability and other derivatives have small effect relatively.