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The influence of elevated water levels on wind field characteristics at bridge sites owing to hydroelectric power stations plays an important role in bridge engineering, particularly in mountainous valley regions. To investigate this issue, a comparative experimental study, which uses a topographic model with two water level states for determining the influence on wind field characteristics at the proposed bridge site located in a mountainous valley area, was conducted in the XNJD-3 wind tunnel at Southwest Jiaotong University, Chengdu, PR China. The altitude difference between the two water level states was approximately 200 m, whereas uniform and D-type boundary layer air inflow conditions were adopted during the wind tunnel test, respectively. The wind speed at the bridge girder and profile of the 1/4, mid, and 3/4 spans were recorded during the experiment. The test results indicated that after the water level was raised, the mean wind speed (or speed-up factor) along the bridge girder decreased by approximately 10%, and the values of the wind profile also decreased. However, the wind profile curve shapes remained approximately unchanged, and the wind attack angle was significantly transformed by approximately 5° in certain locations of the bridge girder. Moreover, the variation in the water level had a negligible influence on the turbulence intensities, turbulence integral length scales, probability distribution of fluctuating wind components, and turbulent wind spectra along the bridge girder. Therefore, as the water level in the canyon rises, the wind field characteristics at the bridge site tend to be conducive to bridge safety. Therefore, long-span bridges located in mountainous valley areas should be designed appropriately according to the expected minimum water level of the river. [ABSTRACT FROM AUTHOR]

Due to the complexity of turbulence in mountain valley and lack of research focusing on such type of turbulence fields, which are critical for both buffeting response and vortex induced vibration (VIV) in slender structures, this paper aims to enhance the understanding of turbulence fields in mountain valley by investigating field measurement wind data obtained by a wind tower and a Windcube Lidar. Turbulence intensity, turbulent spectrum and vertical spatial coherence are obtained and analyzed according to the continuous measured data, which are significantly influenced by mountain terrain. Some of these characteristics are compared with current recommended specifications, standards and empirical formulas. The results indicate that turbulence intensity (e.g. probability density function (PDF) distribution, variation with mean wind speed and height) in mountain valley are very different from those recommended by the specifications and standards. It is identified that the Simiu and Panofsky spectral models could induce large discrepancies for mountain valley terrain in China Southwest, while the von Kármán spectral models can still well indicate such terrains. Furthermore, the vertical spatial coherences can be accurately expressed by some empirical coherence formulas for a mountain valley, but it is not feasible to adopt empirical coherence formulas with fixed parameters to represent the realistic coherence at different heights in a mountain valley. Meanwhile, the results have a general applicability for the determination of wind characteristics in the mountain areas of China Southwest. • The turbulence field in a mountain valley is studied based on the data from wind tower and Windcube Lidar. • Turbulence intensity, wind power spectrum, and vertical coherence are studied and compared with the standards. • The parameters of empirical formulas are calculated, and variation of them with wind speed or height are also studied. [ABSTRACT FROM AUTHOR]