Experimental And Numerical Simulation Study On Wind Loads Of Suspension Bridge With Plate-truss Composite Stiffening Girder

With the development of transportation infrastructure construction,more and more long-span bridges are built across rivers,seas and mountain canyons.Wind load often becomes one of the controlling factors in the design of long-span bridges.At present,the wind resistance design of long-span bridges mostly focuses on the situation that the wind is perpendicular to the axes of the bridges,while the case of skew wind is relatively less considered.Based on the engineering background of Yueyang Dongting Lake Second Bridge,The wind loads of plate-truss composite stiffening girders of long-span suspension bridges under skew wind were investigated throug the experimental and numerical simulation.Considering the effect of wind yaw angle,the internal forces and displacements of long-span suspension bridges under wind loads were calculated,and compared with the code method;Finally,the flutter performances of the plate-truss composite stiffened girder and plate-truss separated stiffened girder were compared.The main contents of this paper are as follows:?1?Through the force measurement test of the stiffened girder segment model,the variation of transverse three-component force coefficients and along-bridge resistance coefficients with wind attack angles and yaw angles of stiffened girder in service state and construction state were studied,and the influence of the length of the compensation segment model on the test results is discussed.The expressions of drag coefficients along bridge axis direction with wind yaw angles which were fitted for the in service state and construction state of plate-truss composite stiffening girder are follows:C_fr??=0.016+0.03sin?2.3?-250?and Cfr???=0.010+0.03sin?2.3?-25°?.And the wind loads test results of the bridge along the bridge axis were compared and analyzed with the values of codes in various countries?2?Computational Fluid Dynamics?CFD?was used to study the two-dimensional simplified simulation method of three-component force coefficients of plate-truss composite stiffened girder.By comparing the numerical simulation results of the three-component force coefficients of the cross-section model along the axis of the stiffened girder,it is found that the numerical simulation results of the cross-section model in the range of 1/3?2/3 of the stiffened beam's standard internode length are in good agreement with the experimental values?3?Computational Fluid Dynamics?CFD?method was used to study the aerostatic coefficients of plate-truss composite stiffened girder under skew wind.The effects of simplified method,simulated length,mesh types and turbulence model of plate-truss stiffened girder on the numerical results of static aerodynamic coefficients were studiedand compared with the experimental results.By comparing the results of flow field profiles of two-dimensional section models with those of three-dimensional numerical simulation,the results show that the distribution of vorticity,velocity and pressure around the two-dimensional section model in the middle of the stiffened beam is in good agreement with that of the three-dimensional numerical simulation at the same position of the stiffened beam.?4?Based on the project of Yueyang Dongting Lake Second Bridge,the wind load internal forces and displacements of the bridge were calculated by using the fitting formulas of aerodynamic coefficients of plate-truss composite stiffening girder and the recommended method of wind-resistant design code of highway bridges in China respectively,it was found that the internal force and displacement responses of some key positions of the bridge are more disadvantageous under the action of skew wind,therefore,the influence of wind deviation angle should be taken into account in the static wind load response analysis of long-span steel truss stiffened girder bridges.Finally,the flutter performances of the plate-truss composite stiffened girder and traditional plate-truss separated stiffened girder were compared by segmental model wind tunnel tests,and found that the critical wind speed and angle of attack for flutter instability of the two beams are quite different.