Accurately quantifying the aerodynamic forces acting on vehicles and long-span bridges is critical for assessing the safety of moving vehicles on bridges which are subjected to strong wind. It is necessary to consider the aerodynamic interference between vehicles and the bridge, especially for this with the bluff body section and wind barriers. However, very few investigations have been carried out to find aerodynamic coefficients of vehicles on a bridge with the bluff body section and considering the effect of wind barrier. This article therefore carried out wind tunnel tests to determine aerodynamic coefficients of container truck on a bridge with a π-cross section and wind barriers. The influence of vehicle position in different road lanes of the bridge deck and the aerodynamic interference between vehicles on the aerodynamic characteristics of the vehicle and the bridge are investigated. Different heights and ventilation ratios of wind barrier are taken into consideration to examine variations of aerodynamic coefficients with different wind barriers. Furthermore, the change mechanism in the aerodynamic coefficients of the vehicles is observed by analyzing the wind pressure distribution on the surface of the vehicles. The test results show that the different lane locations of the vehicle affect the aerodynamic coefficients significantly, as well as the aerodynamic interference between vehicles with transverse arrangement or longitudinal arrangement, especially for the side force coefficient. The existence of wind barrier reduces the side force coefficients of the vehicle remarkably. Such effects also vary with the ventilation ratio and height of wind barrier.
This study investigates the fundamental characteristics of the longitudinal wind power spectra at the gorge terrain. First, a simplified V-shaped gorge terrain model, representing usual deep-cutting gorge terrains where long-span bridges usually straddle, was introduced for the wind tunnel test. The longitudinal wind power spectra at the gorge center were analyzed in detail and compared with those of the simulated oncoming wind. Then, a practical calculation method was proposed to directly calculate the power spectra values at the gorge terrain based on the oncoming wind field and minimum wind parameters at the gorge center. Finally, an infield V-shaped deep-cutting gorge terrain model was also introduced for the wind tunnel test, and the obtained wind power spectra further validated the proposed calculation method. The results show that for both gorge terrain models, the power spectra values in the low-frequency range become closer to those of the oncoming wind with the measurement positions moving away from the ground, while good agreements are always found in the high-frequency range for all of the specified measurement positions. The proposed calculation method can calculate the power spectra values at these two gorge terrains with relatively high accuracy. It is hoped that this study can more conveniently provide informative guidelines for determining the wind power spectra values for similar gorge terrains in engineering practices than traditional wind tunnel tests or computational fluid dynamics numerical simulations.
Wind tunnel tests were carried out to measure the wind pressure of a 200 m high natural-draught cooling tower. An analysis of the distribution characteristics of external pressure was then conducted to determine the pressure coefficients Cp(θ, z) in a given wind profile. Finally, the effect on the response of the shell and the buckling safety of the shell, applying the simplified height-constant pressure coefficient Cp(θ) and the realistic pressure Cp(θ, z), was determined. Taking the wind load specified in the code as an example, the influence of the distribution of external pressure on the wind-induced response was further analyzed. The results indicate that the pressure distribution varies with not only the height z but also the circumferential angle θ, and the wind load of both ends of the tower is significantly greater than that of its middle. Moreover, the wind-induced static responses of the tower under the action of the realistic pressure distribution Cp(θ, z) and the simplified approach Cp(θ) are basically consistent, because the wind load distribution is more important than its magnitude for the wind-induced response of cooling tower, and the wind-induced response of the cooling tower is dominated by the local shell deformation.
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