Research On The Wind Characteristics Of The Site Of A Steel Truss Arch Bridge In The West Mountainous Area

In recent years, with the country's western development strategy, bridges have been increasingly building in mountainous region.Wind characteristics of mountain district are very special and complex,and it becomes an emerging point of departure in the structure wind engineering. The existing bridge wind specification applies only to a flat landscapes of the wind conditions for isotropic. Because of the complex mountainous terrain, landforms, the features of wind characteristics may vary so greatly with the specification values that the environmental characteristics of the wind at the bridge site can merely be properly acquired by in-site measurements. Bases on the Daning River Bridge project, this thesis makes a detail research on the Wind characteristics at the bridge site.The main contents of this thesis are as follows:â‘ Using the wind speed and direction acquisition instrument to measure the wind characteristics at the site of Daning River Bridge during one and a half year, the mean wind and pulsating wind data on the bridge site have been abtained.â‘¡Through analysis on the practical measured data,we obtain the result with the variation laws of the mean wind speed varies with height,the characteristics of turbulence intensity,gust factor,turbulence power spectrum and turbulence integral scale,etc.The results of the studies are listed as follows:â‘ There are essential differences in the wind characteristics between mountain and plain areas.The distribution of mean wind speed on the bridge-site does not meet the logarithmic law or exponential function model recommended by standard,the maximum mean wind speed occurred at the 70m height rather than the top.Therefore, the size of the wind speed and the variation laws of the mean wind speed varies with height in the mountainous areas relate to the topography.â‘¡The results of turbulence intensity calculation show that the turbulence intensity at the 10m height on the bridge-site reach 40% or more,even at the 90m height,it is still as high as 20%.This manifests that the pulsating wind have a very serious effect on typical weatern mountain areas, which will cause bridge buffeting.â‘¢The spectrum of level wind velocity in this test is similar to Irwin spectrum, but its peak value of wind speed power spectrum curve shifts to the high frequency band, which is greatly different from Simiu spectrum recommonded by code. While the curve of vertical wind velocity spectrum is different from Panofsky spectrum recommonded by code too. The change rules in vertrical one can be expressed with a formula.â‘£The result of this test show that,the average of forward turbulence integral scale is 48.5m.And the average of transverse turbulence integral scale is 42.1m,only 70% of standard data.