Three-dimensional Flutter Analysis Of Super Long Span Cable-stayed Bridges Considering Nonlinear Effect Of Aerostatic

Modern cable-stayed bridge is developing into an extra long-span,therefore,flutter has become the crucial consideration in design of suspension bridges.However,the aerostatic effect is not fully considered in flutter analysis,and it is irrefragable that this effect on long-span bridge flutter analysis cannot be ignored,and it should be sufficiently taken into account.The study on flutter for long span bridge is reviewed in this dissertation,and a systematic study has been carried out on the imperfection of existing flutter analysis methods.With considering the aerostatic effects,a more reasonable flutter analysis method for long-span cable-stayed bridge is proposed based on existing flutter analysis methods.The main contents of this dissertation are as follows:(1)The calculation formula of eight flutter derivatives are proposed based on the self-excited aerodynamic time curve,which tested by forced vibration device,taking a thin flat plate with an aspect ratio of 40:1 as an example,The flutter derivatives of the thin plate model are tested under 0°.The results agree well with Theodorsen's theoretical solution,verifying the reliability of the device.On this basis,obtain the accurate flutter derivatives of a long span cable-stayed bridge(main span: 1020m)in order to provide accurate aerodynamic parameters for the flutter anlysis.(2)By using ANSYS software,the wind resistant analysis program for nonlinear aerostatic response analysis of long-span cable-stayed bridges is compiled.The analysis of nonlinear aerostatic response for a long span cable-stayed bridge(main span: 1020m)and a long-span cable-stayed bridge of concept design(main span: 1500m)are carried out.The vertical displacement,lateral displacement and torsional angular displacement(additional angle of attack)at each point of the main beam are obtained under the effects of wind speeds of all levels when the initial wind angles of attack are 0°?3°? and 5°.(3)By adopting the MATLAB software,the wind resistant analysis program for multi-mode flutter analysis of long-span suspension bridges is compiled.Then,the three-dimensional flutter analysis of the two cable-stayed Bridges is conducted in order to explore the contribution ratio of vibration mode in the critical state of flutter.(4)By introducing the upper and lower bounds of the critical wind speed of the flutter and the precondition matrix of structural deformation,Three-dimensional flutter frequency domain analysis method considering the non-linear effect of static wind is proposed and programmed.Based on the above analysis,the flutter analysis considering the non-linear effect of the static wind on the two cable-stayed bridges was carried out,and the chatter of two cable-stayed bridges under different initial wind angles of attack(0°?3°? 5°)was obtained.The magnitude of the critical wind speed,the participation of each vibration mode,and the contribution ratio of each mode energy;Finally,comparing the results of the analysis,the effect of static wind nonlinear effect on the 3d flutter performance of a large span cable-stayed bridge is discussed.The necessity of considering the non-linear effect of static wind(additional attack angle)in the process of three-dimensional flutter analysis for long-span and super-span cable-stayed bridges is described.