Flutter Analysis Of Long-Span Suspension Bridges In The Whole Construction Process Considering The Effects Of Lateral Motion And Static Wind Nonlinearity

The research on the completion phase of the long-span suspension bridge is relatively perfect,but there are few static wind response analysis and flutter analysis considering the static wind nonlinear effect in each construction stage;Most frequency-domain flutter studies are based on 8 chatter derivatives,and it is rare to consider 18 flutter derivatives.With the increasing span of suspension bridge,the dynamic characteristics and additional angle of attack caused by the static wind effect will become more and more prominent,and the lateral degree of freedom will participate in the chattering.Therefore,based on the three-dimensional flutter frequency domain analysis theory,considering the influence of 18 flutter derivatives and static wind nonlinearity,the flutter analysis of long-span suspension cable in each construction stage is carried out.The research steps of this thesis are as follows:(1)Divide the construction stage of the main beam frame facility,establish its finite element analysis model,calculate its structural dynamic characteristics,and obtain the modal frequency of each construction stage;(2)A program for nonlinear response analysis of large static wind is developed.Based on the wind tunnel test,the three-component force coefficients of the main girder section in the completed and constructed state are measured,and the program is used to analyze the static wind stability considering the static wind nonlinearity and the structural nonlinearity under different attack angles.The lateral,vertical and torsional displacements of the main girder under different wind loads are obtained.At the same time,the change of the dynamic characteristics of the structure with the wind speed and the influence of the wind load of the main cable and the wind load of the main tower on the static wind stability are calculated.(3)The frequency domain analysis program of three-dimensional flutter is developed.By using the forced vibration device,8 flutter derivatives of the bridge and the construction state are measured in the wind tunnel by the method of forced vibration test in different states,and all 18 flutter derivatives are derived by combining the quasi steady theory and the three component force coefficient.On this basis,the critical flutter wind speed,mode participation and modal energy contribution in different stages of bridge construction and different angles of attack are calculated.At the same time,the critical flutter state under 8flutter derivatives and 18 flutter derivatives are compared and analyzed from the perspective of modal participation.(4)Considering the influence of dynamic characteristics and additional angle of attack,the program of flutter frequency domain analysis is compiled.The flutter stability of long-span suspension bridge is calculated only considering the additional angle of attack,considering the change of additional angle of attack and dynamic characteristics,and compared with the results without considering the static wind nonlinearity.The influence degree of the dynamic characteristics changing to the additional angle of attack on the flutter stability is obtained,which shows the necessity of considering the static wind nonlinearity.