Wind-environment Actual Measurement And CFD Numerical Simulation Of A Suspension Bridge In The Western Mountains

After entering 21 st century, infrastructure construction in China has been increasingly developed, and the traffic network becomes more and more complicated.The implementation of the western development strategy, especially, brings new vigor and vitality to the west construction in our country. The span becomes larger and larger and the patterns become more and more diversified in the large bridge construction.However, because of the complexity of the western mountain terrain itself, the difference in the regional wind-environment characteristics is evident. And as for long-span bridge, the characteristic of wind resistance is always the priority among priorities in the bridge design. Plus, in order to determine the basic wind speed of bridge design, bridge wind profile and the characteristic of bridge fluctuating wind are the basis when the bridge designer think about wind induced vibration of bridge structure,as well as the first question in bridge design.The wind-environment research relies on the construction of Cuntan Yangtze River Bridge(which spans 880 m as a suspension bridge). And the wind-environment parameters are calculated by analyzing the measured wind speed data and make use of the large fluid calculation software Fluent to conduct the wind numerical simulation in bridge site.The analysis procedures of field measured wind speed are mainly as follows: first,install an anemograph every other 10 meters between the construction pylons in the field bridge tower; then place the wind speed acquisition instrument in the middle of the pylons, and collect the wind speed data every other certain time; at last, conduct the statistic analysis of the wind speed data in order to get the actual measured characteristic of wind field in bridge site. The main characteristics of the wind field include fluctuating wind characteristic as well as average wind. The characteristic of average wind includes the determination of the basic wind speed during 100 year return period, getting the changing law of average wind direction and wind attack angle varying with time as well as the wind rose diagram; while fluctuating wind characteristic mainly studies the turbulence intensity, gust factor of the fluctuating wind velocity, integral length scale and adopt and regulate consistent wind speed spectrum to get the actual wind power spectrum in the bridge site.The analysis procedures of characteristics of wind field from the perspective ofnumerical simulation, first of all, use Google map to get the accurate 3D terrain coordinate value of the bridge site, and then make use of Imageware software to conduct the free-form surface fitting of the 3D terrain coordinate value to get the topographic map of the bridge site, and import the map to Gambit, the pre-processing software of Fluent, to build the wind field in the bridge site model, and after that use the function of mesh generation to mesh generate the numerical wind field, and export the Mesh file. Then, set up the relevant calculation parameters in Fluent, and import the entrance wind profile by the built-in program UDF of Fluent in order to do the computation in 3D wind field, and finally get the velocity contour of the bridge floor as well as a series of important results. Conduct a contrastive analysis of the calculated result and result from the measured data with the code value, and get the actual wind environment characteristic parameters.