| With the development of economy,the built bridges in some areas are gradually unable to meet the increasing traffic demand,so it is necessary to broaden the existing bridges or build new bridges near the existing bridges.For long-span bridges,due to the small spacing between the existing and new bridges,they will inevitably be affected by aerodynamic interference effects.Compared with single bridges,their static wind stability,vortex-induced vibration characteristics and flutter stability may become more unfavorable.Therefore,taking the actual project as an example,this paper uses the combination of wind tunnel test and numerical simulation to study the aerodynamic interference effects of vortex-induced vibration characteristics and three-component coefficients of the proposed new bridge with double existing bridges.The main research contents include :(1)The finite element software ANSYS is used to calculate the dynamic characteristics of the new bridge to be built in the actual project.The first-order vertical bending frequency and torsion frequency,as well as the corresponding equivalent mass and equivalent moment of inertia are obtained.According to the calculation results and test conditions,the 1 : 50 segment scale model is made.A special fixture is designed to adjust the lateral position,vertical position and different wind attack angles of the double-width existing bridge model.(2)The aerodynamic interference of the double-width existing bridge on the drag coefficient,lift coefficient and lift moment coefficient of the new bridge under different lateral spacing ratios was studied by wind tunnel force test.The aerodynamic interference law of the three-component force coefficient at the angle of attack of-10 ° to 10 ° when the proposed new bridge is located upstream and downstream respectively is obtained.(3)The wind tunnel vibration test is used to study the aerodynamic interference of the vortex vibration characteristics of the new bridge under different lateral spacing ratios,vertical spacing ratios and different wind attack angles.The influence law of the maximum amplitude interference factor and the vortex vibration locking interval interference factor under various influencing factors when the proposed new bridge is located upstream and downstream respectively is obtained.(4)The wind tunnel pressure test was used to study the aerodynamic interference phenomenon of the vortex-induced vibration characteristics of the new bridge under different transverse spacing ratio,vertical spacing ratio and different wind attack angles.Through the comparative analysis of the average wind pressure coefficient and the fluctuating wind pressure coefficient on the surface of the model,the aerodynamic interference phenomenon under various working conditions was explained by combining the amplitude and the predominant frequency of the vertical vortex excitation force and the torsional vortex excitation force spectrum.(5)Numerical simulation method is used to study the aerodynamic interference phenomenon of typical working conditions under different lateral spacing ratio,vertical spacing ratio and different wind attack angles.The instantaneous vorticity map,instantaneous pressure cloud map and streamline map obtained by numerical simulation in a period explain the vertical and torsional vortex vibration of a single new bridge and the vortex vibration aerodynamic interference mechanism of each representative working condition. |
