Refined Flutter Analysis Of Long Span Suspension Bridge Considering Aerostatic Effects And Spanwise Correlation Of The Self-excited Forces

Modern suspension bridge is developing into an extra long-span,therefore,flutter has become the crucial consideration in design of suspension bridges.However,the spanwise correlation of aerodynamic forces and the aerostatic effects are not fully considered in flutter analysis,and it is irrefragable that their effects 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 spanwise correlation of aerodynamic forces and the aerostatic effects,a more reasonable flutter analysis method for long-span suspension bridges is proposed based on existing flutter analysis methods.The main contents of this dissertation are as follows:(1)The flutter derivatives identification program is compiled based on the existing forced vibration method for identification of flutter derivatives of two degree of freedom bridge section model.After the flutter derivatives are acquired,the least squares normal equation is applied to identify the rational function at multiple attack angles simultaneously,which provides a new way to identify the rational function.(2)By using the method of surface pressure synchronous measurements which is based on forced motion device in wind tunnel,the spanwise correlation of motion-induced aerodynamic forces of a rectangular cylinder with side ratio B/D=5 and a streamlined box girder with side ratio B/D=1 1.08 are investigated,and the rationality of ’strip assumption’ is demonstrated.(3)With considering the spanwise correlation of aerodynamic forces,a flutter analysis method for torsional single degree of freedom is proposed specially for bluff body.(4)By using ANSYS software,the wind resistant analysis program for nonlinear aerostatic response analysis of long-span suspension bridges is compiled.The analysis of nonlinear aerostatic response for a simply supported suspension bridge with single span(main span:1050m)and a continuous suspension bridge with three spans(main span:1660m)are carried out.(5)By adopting the MATLAB software,the wind resistant analysis program for multi-mode flutter analysis of long-span suspension bridges is compiled.(6)By considering the aerostatic effects and effectively combining the aerostatic analysis program and the multi-mode flutter analysis program,a multi-modal flutter analysis method of long span suspension bridge with streamlined box girder is presented.Based on the above analysis,the detailed flutter analysis of a simply supported suspension bridge with single span and a continuous suspension bridge with three spans were carried out by using the presented method.Finally,the influence mechanism of aerostatic effects on flutter is expounded in terms of the work done by aerodynamic forces.