Numerical Analysis On3D Flutter Instability Of Long-span Suspension Bridges And Effects From Active Controlled Wind Barrier

With the increasing of main span of long-span bridges, wind-induced vibrations become more obviously and therefore become one of key factors in design of long-span bridges. The active controlled wind barrier plays a great significant role on increasing the limiting wind speed of vehicles on bridge deck with less affection on aerodynamic performance of long-span bridges.In this dissertation, a complete numerical analysis on3D flutter instability of long-span bridges has been studied, which consists of two parts: flutter derivatives identification based on "The numerical wind tunnel" and flutter critical wind speed identification based on numerical analysis. This complete numerical analysis can effectively avoid some disadvantages of traditional wind tunnel test, such as high cost, complex test method, long test period and etc. Furthermore, the effect of the existing of active controlled wind barrier and vehicles has been discussed. The main works are as follows:1.3D finite element model of a long-span suspension bridge has been established and analysis on dynamic characteristics of this bridge in completion state have been carried out based on large displacement pre-stressing mode analysis method. Then, the effects of two simulation methods for bridge girder and different ways of arrangement of vehicles on dynamic characteristics of bridge in completion state have been studied.2. A least-square method in time domain on18flutter derivatives identification has been derived in matrix forms, and then programmed based on MATLAB.3. Unsteady aerodynamics of two classical types of girder has been calculated based on forced vibration method,"The numerical wind tunnel" and dynamic mesh technique. Then, flutter derivatives of each type of girder have been identified based on the least-square method. The validity of the numerical method in this dissertation on flutter derivatives identification has been verified by being compared with theoretical or wind tunnel test result.4. A multimode flutter analysis method and a full-order flutter analysis method in frequency domain has been derived and programmed based on MATLAB, then a new method in time domain based on ANSYS has been introduced. Furthermore, the validity of numerical method and program in this dissertation has been verified by identifying the flutter critical wind speed of a classical example.5. The complete numerical analysis has been used for studying the3D flutter instability of the Runyang suspension bridge Then the effects of existing of the active controlled wind barrier and vehicles on the flutter instability of the Runyang suspension bridge has been discussed.