西部河谷地区三水河桥址风场特性试验研究

以三水河特大桥为工程背景,通过风洞试验研究了西部河谷地区桥址处风场特性,分析了西部河谷地区不同风向来流时桥址处风剖面、湍流强度、积分尺度及脉动风功率谱变化情况。通过梯度风速相似关系,结合规范梯度风速,提出由风洞试验实测桥址处风剖面指数及梯度风高度反算桥梁设计基准风速的方法。试验结果表明:当来流与河谷走向一致时风剖面接近幂指数分布,其他风向角风剖面不能用统一的幂指数分布表示,河谷风平均风剖面指数较其他风向小,拟合得到指数为0.142;河谷内的湍流度比较大,特别是在接近边坡的位置,桥面高度跨中的湍流度大于15%;由于桥梁结构位于河谷内,平均风速在来流风速的基础上被衰减而非放大,桥址处无明显的峡谷风效应;湍流积分尺度与脉动风功率谱的变化需要考虑周围山地的影响。

Experimental study on wind field characteristics of Sanshui river bridge site located in west valley region

Taking Sanshui river bridge as an engineering background,the wind field characteristics of the bridge site located in the west valley region were derived through the wind tunnel test of a terrain model.The changes of wind speed profile,turbulence intensity,turbulence integral scale and turbulence spectrum in different wind directions in west valley region were analysed.According to the similarity relation related to the gradient wind speed,and referencing the gradient wind speed stipulated in the wind-resistant design code,a method of calculating design wind speed of bridge in agreement with the wind speed profile and the magnitude of the gradient wind speed measured at the bridge site in wind tunnel test was proposed.Test results show that the wind speed profile is of a power-law distribution,when the coming wind is parallel to the trend of the valley.The wind speed profile in other directions cannot be simulated by a uniform power-law relationship.The power exponent of wind speed profile parallel to the trend of the valley is less than those in other directions,and the value is equal to 0.142.The intensity of turbulence in the valley is the largest,especially near the side slope,and the value is bigger than 15% at the upper part of bridge deck near midspan.The wind speed is attenuated rather than amplified compared to the coming wind speed.Because the bridge is located in the valley,so the bridge site has no notable magnification effect on wind speed.When considering the turbulence integral scale and turbulence spectrum,the shape of mountain on both sides should be taken into account.