Research On Fluid-structure Coupling Effect Of Two-span Simply Supported Suspension Bridge With π Girder

Theπgirder two-span simply supported suspension bridge has low overall rigidity.Theπsection has weak torsion resistance and poor streamline.The interaction between separated flow and vortex shedding is more complicated.Therefore,the large-span cable supported bridge withπsection is prone to aerodynamic resonance under the effect of fluid-solid coupling.In view of the above reasons,it is necessary to study the wind resistance performance of the two-span simply supported suspension bridge withπgirder.In this paper,the numerical wind tunnel is used to complete the identification of the three-component force coefficient and flutter derivatives of theπsection;The three-dimensional flutter response simulation of the two-span simply supported suspension bridge structure is carried out to study the flutter performance of the bridge structure considering the fluid-solid coupling effect;Based on the turbulence model k-ωSST,the fluid-structure coupling simulation of the vortex-induced vibration of theπgirder bridge was carried out,and the vortex vibration sensitivity of the main girder suspension bridge of this type was studied.The main research work and conclusions include:（1）Using the original scripting language engine,theπsection static flow simulation was realized by programming,and it was verified with the ideal flat plate and the closed box girder section.The agreement between the simulated values of the slab lift and the lift moment coefficient and the theoretical solution is above 95%;the relative error between the simulated value of the resistance coefficient of the closed box girder and the test value is less than 7%,which is less than the upper limit of 15%specified in the design code for wind resistance of highway bridges.The numerical simulation method in this paper is reliable.（2）The flutter derivative identification simulation of theπgirder section was realized,and the ideal flat plate and the closed box girder section were compared and verified.The agreement between the simulated values and theoretical values of the flat plate flutter derivatives H₁*,H₃*,H₄*,A₁*,A₂*is above 94%;the overall curve trend of the simulated values of the flutter derivatives of the closed box girder section of the Jiangyin Bridge and the wind tunnel test values Similarly,the error between the obtained flutter critical wind speed and the wind tunnel test value is within 2.43%,and the error is low.（3）A three-dimensional nonlinear chattering analysis platform for suspension bridges is constructed.Harmonic synthesis method is used for wind field simulation;nonlinear chattering time-domain method is used to calculate structural chattering response,taking into account the influence of structural geometric nonlinearity and aerodynamic load nonlinearity;through the establishment of self-excited time-domain wind The load model considers the fluid-structure coupling effect.The results show that theπgirder double-span simply supported suspension bridge in this paper has a small structural displacement under the design wind speed,which meets the requirements of pedestrian comfort,and is rated as"good".（4）Programming is based on an original script language,a turbulence model is selected,and a staggered method is used for fluid-solid coupling processing.A numerical simulation method for the vortex-induced vibration of aπcross-section main beam is realized based on the large-deformation dynamic grid and the finite volume method;this method is used for rectangular column k-ωSST vortex-induced resonance search was carried out.The results of the rectangular column vortex-induced resonance simulation and wind tunnel test showed that the error of the maximum vortex vibration amplitude was not more than 6.8%,and the difference in the wind speed lock interval was small,which verified the reliability of the method in this paper;The suspension bridge was tested by vortex-induced resonance,and the wind speed range of4-28m/s was searched under the condition of 0.008 damping ratio.It was found that the bridge had a vortex-induced resonance response in the wind speed range of 12-18 m/s.Finally,the correlation between the occurrence of vortex vibration and the damping ratio of this type of bridge is analyzed,and it is found that as the damping ratio decreases,the wind speed range where vortex vibration occurs is basically unchanged,but the maximum vortex induced amplitude changes greatly.When the damping ratio is0.004,the maximum amplitude of the vortex vibration exceeds the specification limit.