Study On The Three-dimensional Buffeting Force And Aerodynamic Admittance Of Streamlined Bridge Deck Considering Effects Of Pylon Shelter Under Skew Wind

In order to meet more complex functional settings and traffic travel,modern bridges are developing in the direction of large span and lightness.The static wind load and buffeting response of bridge decks under the atmospheric boundary layer turbulence are restricted by more factors.The effect of skew wind and the shelter effect of pylon are both important factors in the study of buffeting force of long-span bridges.Therefore,it’s of great significance to study the buffeting force characteristics and three-dimensional aerodynamic admittance recognition considering the shelter effect of pylon under skew wind.Based on the three-dimensional aerodynamic admittance recognition theory of bluff body section,this paper uses the test method of wind tunnel pressure measurement to realize the aerodynamic rigidity model pressure test of the streamlined box girder under different wind attack angles and wind yaw angles in the construction state of the double cantilever cable-stayed bridge under the premise of considering the shelter effect of pylon.In the rigid model pressure test,the static load coefficient and buffeting force characteristics of the bridge under skew wind were further analyzed and studied,and the aerodynamic admittance of two-wave number lift under different wind angles was identified.1.The classic analysis theory of bridge buffeting under the action of skew wind reviewed,the development of aerodynamic admittance function introduced,and the difference and correlation between aerodynamic admittance of aero-wing profile and bridge blunt-body cross-section analyzed,this paper summarizes the current commonly used admittance recognition methods,and points out their advantages and difficult points.2.On the basis of the three-dimensional aerodynamic admittance spectrum tensor theory,the use of the pressure measurement equipment in the wind tunnel laboratory of Chongqing University and the special deflection angle rotating bracket,The aerodynamic rigidity pressure measurement model test in uniform flow and grid turbulent flow field verifies the uniformity of the turbulent wind field and lays the foundation for subsequent buffeting force analysis and aerodynamic admittance identification.3.Based on the bridge static three-component force theory,the changes of lift coefficients and drag coefficients with different wind attack angles and wind yaw angles are obtained by comparing and analyzing the measured values of the static three-component force coefficients of the main girder at different angles of attack and declination.And the "cosine criterion" is proved to be unsuitable for the calculation of the wind load of the main girder under the action of skew wind according to its comparison with the measured value of the wind tunnel test with the three-component force coefficient.4.Based on the theory of three-dimensional aerodynamic admittance recognition of bluff body cross-sections,analyzing the change rules of the aerodynamic parameters of buffeting lift control affected by different variables such as the shelter effect of pylon,wind attack angle and wind yaw angle,the two wavenumber aerodynamic admittance of buffeting lift under the influence of wind considering the shelter effect of pylon is obtained and the mechanism of the influence of the skew wind on the three-dimensional aerodynamic admittance of the streamlined box girder section is revealed.