CFD Numerical Simulation Of Static Gust Effect Of Highway Bridge

The lateral static gust load is calculated only by the static gust coefficient for wind resistance design of highway bridges according to Chinese wind resistance design codes of highway bridges.At the present,considering the wind gust model in the incoming wind speed has been paid more and more attention by researchers on the wind resistance of bridge structures.Long-span continuous rigid frame bridges are more sensitive to wind loads during cantilever construction.Therefore,it is necessary to analyze the displacement response of the cantilever beam under the gust.The main research contents and results of the article are listed in the following.(1)The box girder cross-section of a long-span continuous rigid frame bridge is taken as an example in this paper,and the flow filed characteristics of box girder cross-section under the action of-5°~+5°wind attack angle are simulated and analyzed by Fluent software,the static three-component force of the beam section is obtained.It is concluded that the numerical results basically meet the requirements of the aerodynamic analysis of the box girder section,which verifies the feasibility and accuracy of the numerical simulation method.(2)The gust wind speed time history program is written by the UDF(User Defined Function)function of Fluent software to provide the velocity inlet boundary conditions for flow field calculation.The Fluent software was used to simulate and analyze the aerodynamic characteristics and flow field characteristics of the box beam cross-section when TSI(Technical Specifications for Interoperability)gusty wind and IEC(International Electrotechnical Commission)gusty wind were applied at-5°~+5°wind angle of attack,the time curve of the component force coefficient is obtained.It is concluded that:1)Under the effect of TSI and IEC gusty wind,the time history curve of the three-component force coefficient of the box beam section calculated by CFD generally revolves around the three-component force coefficient based on the quasi-steady assumption,but when the wind attack angle is large,the lift coefficient and moment coefficient fluctuates greatly.2)Under the effect of TSI gusty wind,the drag coefficient has jumps at the peak and troughs of the gust velocity;the change of the lift coefficient lags behind the gust velocity.The overall static pressure of the flow field has adverse pressure gradient and favorable pressure gradient.3)Under the effect of IEC gusty wind,the calculated static three-component force coefficient and the static pressure at the inlet boundary both change continuously,and the favorable pressure and adverse pressure that approximates the overall linear change in the flow field.4)It is considered that the description of the wind filed by the IEC gust model is more reasonable than that of the TSI gust model,and it is more suitable for the numerical simulation calculation of the bridge.(3)The cantilever beam with the same cross-section of 60m is taken as an example,the displacement response of the cantilever beam under the action of IEC gusty wind and different wind angles of attack for lateral and vertical vibration are calculated and analyzed.It is concluded that:1)The displacement response of the cantilever beam during lateral vibration and vertical vibration increases with the distance from the root of the cantilever beam.2)When the cantilever beam vibrates laterally,the displacement response does not change significantly,and the displacement response at each cross-sectional position is a continuous smooth curve;when the wind attack angle is?)82((10)3~?,(10)5~?,the displacement response fluctuates significantly within and during the time period,which is near the location of the IEC gust wind speed trough.3)When the cantilever beam is subjected to vertical vibration,the vertical bending rigidity of the cantilever beam is smaller than the lateral bending rigidity,and the vertical vibration displacement is much greater than the lateral vibration displacement.When the wind attack angle is?)82((10)3~?,(10)5~?,the displacement response at each cross-sectional position fluctuates greatly during the entire process of the IEC gusty wind;the high-frequency fluctuation phenomenon under the positive angle of attack does not exit at the negative angle of attack,and the displacement curve is continuous and smooth curve,displacement response changes are not obvious.