Numerical Simulation Of Aerodynamic Stability Of Large Span Bridges With Closed Streamlined Girder Section

With the promotion of cross-sea bridge project construction and the increase of bridge span,the effect of wind on bridge becomes more obvious and the flutter stabil-ity of long-span bridges has become the focus of wind resistant design of long-span bridges.The aerodynamic stability of the main girder with closed streamline section that widely used in long span cable-stayed bridges and suspension bridges is impor-tant to the flutter stability of bridge,and is always the focus in the field of engineer-ing and research.This thesis mainly takes the Lingding Waterway Bridge of ShenZ-hong Channel Engineering as research object to make numerical simulation of aero-dynamic stability of large span bridges with closed streamlined girder section.The main research work is as follows:(1)The background and significance of the research on the aerodynamic stability of the closed streamline main girder section were presented and the research methods of aerodynamic self-excited forces of long-span bridges were re-viewed.(2)The basic theory of CFD for incompressible flow and the classical aerody-namic model were elaborated,as well as the analysis methods for differential equations and two-dimensional flutter.(3)The numerical simulation method of flutter derivatives identification based on Scanlan linear self-excited theory was established.The flutter derivatives of a thin plate were firstly identified to demonstrate the feasibility of coupl-ing forced vibration method by comparing with those calculated by Theodor-sen theory.Then the flutter derivatives of the Great Belt main girder section were identified.The results calculated agrees well with the existing literature and the test research.Based on the coupling forced vibration method,a new step-by-step multi-frequency method for rapid identification of bridge flutter derivatives was used,which forces model to do complex vibration with multi?frequency in vertical bending and torsion independently so as all of the flutter derivatives under different reduced wind speed were rapidly identified.(4)Analysis method for VIV simulation of simple rectangular section based FSI theory was established in the open source software OpenFOAM,as well as that for flutter simulation of the bridge section,where Fluent was used for solving hydrodynamic equation,sliding mesh combining with dynamic mesh method techniques was used for mesh motion and corrected velocity New-mark belt algorithm was used for solving structure vibration response.Then the simulation of the flutter stability of the main girder of the Original De-sign Scheme of Lingding Waterway Bridge of ShenZhong Channel Engineer-ing was taked,and that of the aerodynamic optimization of main girder sec-tion followed.The results can provide technical support for the wind resistant design for that project.(5)The nonlinear vibration phenomenon in process of the experiment of the main girder with closed streamline section is analyzed preliminarily.The vibration response,frequency spectrum curve,phase plane diagram,etc.under different wind velocity were presented and the influence factors of nonlinear vibration were discussed from the point of section model test.