| The construction of adjacent bridges becomes more and more,and the aerodynamic interference effect between adjacent bridges leads to the difference of static wind load and flutter stability compared from single bridge,which can’t be ignored for long span adjacent bridges.Moreover,the change of wind field caused by aerodynamic interference effects may affect running safety.The aerodynamic interference effect between long span adjacent bridges has become one of the concern points of wind-resistant design.Centering on the aerodynamic interference effect between long span adjacent bridges,researches are as follows:First,the basic theory of computational fluid dynamics and engineering background are introduced,and the static coefficients of the downwind bridge alone is obtained based on CFD numerical simulation,then it is verified through wind tunnel test,which is ensures the method of analysing the aerodynamic interference effect by CFD numerical simulation.Then,the influence of the aerodynamic interference effect on static coefficients and the influence on running wind environment are researched.Based on the practical engineering background,considering the factors of different relative horizontal position and different vertical position,the static coefficients of upwind bridge and downwind bridge and the curve that wind velocity amplification factor changed with height on the center of lane of downwind bridge are calculated by numerical simulation at different wind attack angle(range from-7° to 7°),and make an analysis and discussion on the change of static coefficients of upwind bridge and downwind bridge and change of wind velocity amplification factor on the center of lane and the train centre of gravity of downwind bridge with the aerodynamic interference effect.Finally,the influence of the aerodynamic interference effect on flutter stability is researched.Based on the practical engineering background mentioned in the third chapter,considering the factors of different relative horizontal position and different vertical position,the flutter derivatives of downwind bridge is calculated by numerical simulation in common inflow(0°angle of wind attack)and extreme inflow(7°angle of wind attack),and combined with it,make an analysis on flutter stability from the views of aerodynamic damping and aerodynamic stiffness,furthermore,the critical flutter state is solved by semi-inverse method with MATLAB program,the interference factor of flutter critical wind speed and flutter frequency are obtained,and the influence of aerodynamic interference effect on flutter critical wind speed and flutter frequency is analyzed.The results demonstrated as follows: the the results obtained based on CFD numerical simulation is in good agreement with wind tunnel test,which provides the feasibility for the study of aerodynamic interference effect of adjacent bridges.The aerodynamic interference effect has a weak effect on the lift coefficient and the moment coefficient of the upwind bridge,and the drag coefficient of the upwind bridge is reduced in some degree,the degree of reduction is related to horizontal spacing ratio,height difference and wind attack angle.Aerodynamic interference effect has great influence on the static coefficients of downwind bridge,which is related to horizontal spacing ratio,height difference and wind attack angle,compared with the downwind bridge alone: the drag coefficient can be reduced up to 35.3%,the maximum increase can be reached 12.1%;the absolute value of lift coefficient can be reduced to 74.5%,the degree of improvement can reach 10.0%;the maximum degree of moment coefficient can be reduced to 80.0% and the maximum can be increased to 48.1%.The wind field of the bridge deck of downwind bridge on the center of the lane is similar,which still maintain under the influence of aerodynamic interference effect.The existence of upwind bridge reduces the wind velocity on the train centre of gravity of downwind bridge,which is beneficial to traffic safety,but the difference of wind velocity on the train centre of gravity of downwind bridge along the span direction of bridge(There are different height differences between upwind and downwind bridges),the factor of height difference should be taken into account in wind-vehicle-bridge system vibration analysis according to the situation.The wake flow bypassing upwind bridge has great effect on great influence on aerodynamic damping and aerodynamic stiffness of downwind bridge,which contributes to the greatly impact on flutter stability,even the flutter modality is changed,and This change is related to horizontal spacing ratio,height difference and wind attack angle.Specifically: At a small angle of attack(0°),the flutter modality of the downwind bridge is bending-torsional coupling,compared with that of the downwind bridge alone,the degree of reduction of critical flutter wind speed can be as high as 11.7%,and the maximum increase degree of flutter critical wind speed can reach 23.7%,aerodynamic interference effect is to increase the flutter frequency of the downwind bridge,which can be increased by 36.3% at most.At a small angle of attack(7°),the flutter modality of downwind bridge with height difference of 3m and 5m is bending-torsional coupling,the flutter modality of downwind bridge with other working condition and the downwind bridge alone is torsional,compared with that of the downwind bridge alone,the flutter critical wind speed can be reduced up to 13.2%,the flutter critical wind speed up to 59.5%,the flutter frequency of the downwind bridge is not sensitive to the change of horizontal spacing,and the flutter frequency can be reduced to 10.0% by the influence of height difference. |
