| The area of mountain ridge accounts for the most part of our country land. With the development of economic construction, more and more long span bridges have been built in the mountainous region of the western in China. In order to guarantee the safety of the structure during the phase of construction and operation, the wind load acting on the structure must be studied. But in the existing anti-wind specification the parameters of wind characteristics on complicated mountain, gorge and mountain pass terrain have no explicit stipulation, such as law for change of wind speed and wind pressure under the influence of topographic effect, value of wind attack angle, distribution rule of wind profile, law for change of turbulence intensity and gust factor. The investigation into the wind-environment of bridge on complex mountain-valley terrain involves these factors, such as geometry of structure, plane position, height, direction of inflow, surrounding terrain, upstream landform etc. Being lack of the research reserves, the designer can't accurately forecast the wind-induced response of the structure on the complex terrain. So it is obviously significant to study the wind characteristics on complicated terrain.Theoretical basis of bridge wind environment is comprehensively studied in this dissertation. Based on the method of data statistical analysis, a data processing system of wind speed observation V1.0 based on Borland C++ Builder is developed, which can rapidly and automatically process massive data.It's the first time to put the wind field observation of special topography on the upper and middle yellow river into practice. Through 3 wind observation towers on the bridge site, the field measured data of Yellow River great bridge of YuMenkou for one year and a half has been obtained. Strong wind characteristics such as, the mean wind velocity, direction, turbulence intensity and turbulence integral length are obtained. Meanwhile the specific wind space distribution and regular pattern around the bridge on gap of valley areas are firstly gained:①wind speed on the bridge site is increased by the influence of gorge wind effect;②the value of wind attack angle is larger than that on plain area and the range is 9°～-8°;②the application of wind profile can't directly use the specific and must be fitted by measured data;④turbulence intensity and gust factor are smaller than the value on common strong wind condition.Wind field of terrain liking bell where the river flows from canyon to the open field have been firstly simulated by CFD. Wind-environment Numerical Simulation Based on the technique of numerical wind tunnel firstly adopts Realizableκ-εand SSTκ-ωturbulence modes to model with the two situations whether there is bridge model and imitates the bridge site and the wind field under 7 working conditions. The distribution of wind profile, wind-velocity streamline, pressure streamline and turbulence are obtained and the results are compared with that of wind field measurement. The law for change of wind speed and turbulence with the variation of height is summarized and the situation of flow around wind environment on bridge site is obtained. The result of analysis testifies the correctness and efficiency of the numerical method.Combining live observed wind with numeric simulation, the wind characteristics on the western gap of valley areas are firstly studied. The law for change of wind environment and the situation of wind flow around bridge are summarized, In the meantime, the influence of the bridge built up on wind characteristics is analyzed and advices on both turbulence integral scale and the model of wind profile are given. So the studies of inland wind environment may utilize it as reference materials. It would be provided with great theoretical significance and practical engineering value passes through the foregoing study. |
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