Field Measurement And Research For Wind Parameters Of Cable-stayed Bridge With Steel Box Girder

Few domestic and foreign scholars study field measurement of wind parameters at the large-span steel box girder, especially wind characteristics research at the bridge site under the typhoon weather are less. So this paper relies on "twelfth-five" major scientific and technological projects of department of transportation, the topic name is wind rain effects monitoring and simulation research of the large bridges of wind rain coupling observation and extraction technology research. Pilot group install wind pressure measurement system on Xia-Zhang Bridge and extract air wind pressure and wind parameters data by bridge health monitoring system. Meanwhile, this paper analyze wind parameters data and research the law of the wind farm at the bridge site, and based on CFD modeling, and analyze the case of the wind farm around the bridge, and provide useful reference for future wind field measurement parameters of the large-span steel box girder. By this measurement, calculation and analysis, this paper obtains the following results:First, this project successfully develops a set of measurement system for steel box girder outer surface wind pressure. It contains description of the measurement systems theory, detailed design of the measurement system, detailed installation steps of the measurement system, testing method of the measurement system. By designing a sensor inlet shutter means this paper solves the problem which inlet is vulnerable to attack and clogged by rain. By using excessive slope method this paper also solves the contradiction which wind pressure tube can not be embedded in the bridge beam. At the same time, the paper gives a wind pressure tube reference diameter and length by the laboratory experiments and verifys the permanent magnets had no effect on low frequency electrical signals, also gives two different methods to determine the initial value.Second, according to analyzing field data we find that it will have the effect of wind flowing around when wind past the bridge beam. To find out the law of the effect of wind flowing around, this paper carries on numerical simulation analysis bases on CFD method. Through the data analysis of the results of the model, it is found that there is a linear relationship between distal wind velocity and wind velocity at the anemometer, and there is also approximately a linear relationship between distal wind angle of attack and wind angle of attack at the anemometer. There is an exponential relationship between the arrangement of the height of the three-dimensional anemometer and wind angle of attack that is measured. When the height of the anemometer is fixed, the relationship between the distal wind angle of attack and wind angle of attack that is measured can be approximated by a linear relationship and the relationship between the distal wind velocity and wind velocity at the anemometer can also be approximated by a linear relationship. Also found that, when the wind speed is greater than 25m/s, the value of the wind angle of attack in the wind farm fixed position will be stabilized.Third, through analyzing the wind characteristics of the typhoon "Matmo" we find that the upwind wind velocity, wind angle of attack, wind direction are relatively stable, and the leeward side is relatively disordered, large fluctuations. The windward side’s angle of attack is generally positive, and the leeward side of the angle of attack is generally negative, so it confirms the effects of wind flowing around what the second chapter elaborates. Turbulence intensity values measured of the Typhoon " Matmo" with an average of Iu=0.146, Iv=0.140, Iw=0.090(Iu:Iv:Iw=1:0.96:0.62) compare with specification values is large. Turbulence intensity and gust factor that is measured by the both sides anemometer is larger different, and it also shows that wind characteristic changes significantly when wind through bridge beam, namely the effect of wind flowing around.Fourth, real and reliable law of wind pressure distribution is obtained by field measurement. By analyzing pressure distribution around the steel box girder under the different wind velocity, wind angle of attack, wind direction can be found that the most sensitive parts of wind pressure is in the corner of the steel box girder, and maintenance car track at beam bottom can cause mutations pressure, and wind pressure of the beam bottom presents linear trend, and leeward side’s pressure is relatively insensitive.