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The topography of mountainous areas is characterized by large undulations, which lead to a very complex wind field at bridge sites in mountain valleys. The influence of oncoming wind speed on long-span bridges built in mountain valleys is quite pronounced. To investigate the wind characteristics at a bridge site in a mountain valley under different oncoming wind speeds, a wind tunnel test of a terrain model with a scaling ratio of 1:1000, where a long-span bridge would be built in the V-shaped canyon, was conducted. Uniform and atmospheric boundary layer (ABL) inflows were both applied, and the effect of different oncoming wind speeds (basic wind speeds of 6 m/s, 8 m/s, 10 m/s, 12 m/s, and 14 m/s) under three wind directions (0°, 30°, and 180°) on the wind characteristics at the main beam and two bridge towers were studied. The results indicate that increasing oncoming wind speed leads to decreased wind profiles and wind speed amplification factors and increased wind attack angles, while wind yaw angles remain largely unchanged. In addition, compared to ABL inflow, the variation of fluctuating wind characteristics is more pronounced with the oncoming wind speed under uniform inflow. Under uniform inflow conditions, increasing the oncoming wind speed causes decreased turbulence intensity, reduces the peak frequency of the power spectrum, and slows down the high-frequency decay rate. Under ABL inflow conditions, turbulence intensity and the power spectrum remain unchanged with different oncoming wind speeds. Additionally, the turbulent integral scale derived from fitting with the von Kármán wind spectrum is sufficiently accurate, and the variation in the turbulent integral scale is greatly influenced by the terrain. Furthermore, higher wind speeds result in stronger coherence between two points. When two points are at different locations but with the same spacing, the coherence function remains roughly the same. Locations with higher kurtosis and skewness values exhibit steeper probability density functions, with larger kurtosis and skewness coefficients typically found on the leeward side. High wind speeds are more detrimental to bridge safety, and appropriate preventive measures should be implemented in advance to address extreme conditions that may arise at high wind speeds. [ABSTRACT FROM AUTHOR]

The topography of mountainous areas is characterized by large undulations, which lead to a very complex wind field at bridge sites in mountain valleys. The influence of oncoming wind speed on long-span bridges built in mountain valleys is quite pronounced. To investigate the wind characteristics at a bridge site in a mountain valley under different oncoming wind speeds, a wind tunnel test of a terrain model with a scaling ratio of 1:1000, where a long-span bridge would be built in the V-shaped canyon, was conducted. Uniform and atmospheric boundary layer (ABL) inflows were both applied, and the effect of different oncoming wind speeds (basic wind speeds of 6 m/s, 8 m/s, 10 m/s, 12 m/s, and 14 m/s) under three wind directions (0°, 30°, and 180°) on the wind characteristics at the main beam and two bridge towers were studied. The results indicate that increasing oncoming wind speed leads to decreased wind profiles and wind speed amplification factors and increased wind attack angles, while wind yaw angles remain largely unchanged. In addition, compared to ABL inflow, the variation of fluctuating wind characteristics is more pronounced with the oncoming wind speed under uniform inflow. Under uniform inflow conditions, increasing the oncoming wind speed causes decreased turbulence intensity, reduces the peak frequency of the power spectrum, and slows down the high-frequency decay rate. Under ABL inflow conditions, turbulence intensity and the power spectrum remain unchanged with different oncoming wind speeds. Additionally, the turbulent integral scale derived from fitting with the von Kármán wind spectrum is sufficiently accurate, and the variation in the turbulent integral scale is greatly influenced by the terrain. Furthermore, higher wind speeds result in stronger coherence between two points. When two points are at different locations but with the same spacing, the coherence function remains roughly the same. Locations with higher kurtosis and skewness values exhibit steeper probability density functions, with larger kurtosis and skewness coefficients typically found on the leeward side. High wind speeds are more detrimental to bridge safety, and appropriate preventive measures should be implemented in advance to address extreme conditions that may arise at high wind speeds.

Long-span bridges in mountainous areas are greatly disturbed by wind, and the wind field at the mountain gorge bridge site is extremely complex. Therefore, it is of great engineering significance to accurately evaluate the wind field characteristics of this kind of terrain. In this paper, to enhance understanding of this kind of wind field, the wind field in a mountainous gorge is measured for a long time using wind radar, and the mean wind parameters are statistically analyzed. The results show that the mean wind parameters vary greatly under different wind directions, and the wind speed profile does not meet the power-law model. Therefore, a mixed model suitable for the wind speed profile in a mountainous gorge is proposed. Additionally, GEV distribution and Logistic distribution are found to be suitable for describing the distribution characteristics of wind speed and angle of attack, respectively. In addition, considering the correlation between wind parameters, this paper also constructs the joint probability model of wind speed and angle of attack at different heights by the Copula function. Thus, a combined wind parameters profile model is developed under different exceedance probabilities based on the inverse first-order reliability method (IFORM). This study can provide a reference for the construction of the joint probability model of wind parameters. [ABSTRACT FROM AUTHOR]

Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. The wind characteristics of the mountainous environment in Western China are extremely complex. Many advances have occurred in the study of wind characteristics in plains or hilly areas. However, some limitations remain in the study of mountain passes and riverbanks. We selected a mountain pass and river beach in a certain area as the research objects, then set up observation instruments at different locations to establish temporary observation stations to collect more than one year of measured data. By processing the measurement data during the observation period, the mean wind characteristics and fluctuating wind characteristics of the area were obtained. Through comparison with the standard, we found strong nonstationary characteristics of the wind, such as large deviations between the wind field characteristics values in the standard and measured values, proving the need for wind field observations of mountain passes and riverbanks. [ABSTRACT FROM AUTHOR]

The wind characteristics of the mountainous environment in Western China are extremely complex. Many advances have occurred in the study of wind characteristics in plains or hilly areas. However, some limitations remain in the study of mountain passes and riverbanks. We selected a mountain pass and river beach in a certain area as the research objects, then set up observation instruments at different locations to establish temporary observation stations to collect more than one year of measured data. By processing the measurement data during the observation period, the mean wind characteristics and fluctuating wind characteristics of the area were obtained. Through comparison with the standard, we found strong nonstationary characteristics of the wind, such as large deviations between the wind field characteristics values in the standard and measured values, proving the need for wind field observations of mountain passes and riverbanks.

Abstract This paper investigates the wind characteristics along the bridge catwalk during construction in a deep-cutting gorge. Five sets of anemometers are installed in the catwalk to collect field measurements. The mean wind characteristics, including wind speed and wind direction, are first investigated. The influence of local topography on the mean wind characteristics is identified. Moreover, it is also found that the recorded wind data obtained from the deep-cutting gorge have strong nonstationary characteristics. Based on the traditional stationary wind speed model and a nonstationary wind speed model, turbulence wind characteristics, such as turbulence intensity, spectral analysis and turbulence length scale, are comprehensively analyzed and compared. The effect of local topography on the turbulence wind characteristics is also examined. Additionally, the change laws of turbulence intensity and turbulence length scale along the bridge catwalk are derived. The estimated auto-spectral density functions of all three turbulence components are in a good agreement with the Von Kármán forms. Highlights • Five sets of anemometers are installed to collect field measurements. • Both mean and turbulence wind characteristics are analyzed. • Influence of the local topography on the wind characteristics is identified. • Wind data have strong nonstationary characteristics in such deep-cutting gorge. [ABSTRACT FROM AUTHOR]

Affected by the large-scale boundary layer wind, thunderstorm clouds are often accompanied by a horizontal movement while producing downdrafts. However, previous studies mainly focused on the stationary downburst. Hence, the understanding of the wind field characteristics of moving downbursts is still insufficient. To study the influence of a storm's movement on the downburst wind field, based on the impinging jet test device with a movable nozzle, the stationary and moving downburst are simulated. Firstly, the moving average method is used to process the wind speed time history, and according to various existing criteria, a reasonable moving average time is determined. Afterwards, the vertical, radial, and lateral wind profiles are respectively given, and the influence of the parameter η – which represents the ratio of the storm translating speed (V tr) to the jet velocity (V jet) – on the wind profile is studied. Moreover, the applicability of the vector sum method is verified. Finally, turbulence properties including turbulence intensity, power spectral density function (PSD), and probability density distribution function (PDF) are furthermore analyzed. • The characteristics of stationary and moving downburst wind profiles are comprehensively analyzed. • The effect of the ratio of moving velocity to jet velocity on the wind field is studied. • Verified the applicability of the vector sum method. • The turbulence properties of stationary and moving downbursts are compared. [ABSTRACT FROM AUTHOR]

• The wind characteristics near a river in a mountain valley based on the wind data collected from two masts located at different positions (i.e., the hillside and bottom of the canyon) is comprehensively investigated. • Mean wind speed, mean wind direction, turbulence intensity, gust factor, wind power spectrum, and vertical coherence are studied and compared with the specifications and standards. • The wind characteristics measured at different positions (i.e., the hillside and bottom of the canyon) are compared and studied, which is of great significance to the selection of wind mast position. The characteristics of wind in mountain valleys are complex; in this paper, we present a comprehensive analysis of these characteristics using data obtained from two wind masts located at hillside and at the bottom of a canyon. In view of the limited literature focusing on the effect of the location of measurement on the characteristics of wind in mountain valleys, we present a comparison of these characteristics in this paper. The wind characteristics investigated in this study include the mean wind speed, mean wind direction, turbulence intensity, gust factor, wind power spectra, and vertical coherence. The results indicate that the mean wind speed, turbulence intensity, and wind power spectra cannot be predicted accurately using specifications or standards. The mean wind direction at a high wind speed is always along the canyon. A modified exponential coherence model can depict the vertical coherence effectively. Furthermore, wind characteristics are to some extent affected by the variations in height and locations of measurement, but still valuable for engineering practice, and a 30-m wind mast can meet the needs instead of a 50-m one. [ABSTRACT FROM AUTHOR]