高海拔高温差深切峡谷桥址区日常大风成因

Causes of Daily Strong Wind on Bridge Site in Deep Gorge with High Altitude and High Temperature Difference

为探讨高海拔高温差深切峡谷桥址区日常大风的成因,采用CAW600-RT型四要素自动气象站、手持风速仪及便携式温度计,对大渡河大桥桥址区风特性进行实测,分析了桥位处平均风速与温度、日照及地形地貌等的相关性.结果表明:大渡河大桥位于高海拔高温差深切峡谷内,桥址区几乎每天下午起风,平均风速常达10 m/s以上;根据成因,桥位处的大风可分为2类,一类受大尺度大气环流影响,另一类受小尺度范围内热力驱动而产生日常大风,并受局部地形及随时间变化的日照的影响;桥位处日常大风出现的频率较高,虽不控制桥梁的设计基准风速,但影响桥梁的耐久性和行车舒适性.

In order to investigate the causes of daily strong wind on a bridge site in a deep gorge with a high altitude and a high temperature difference,the field measurement of wind characteristics was carried out on the Dadu River bridge site with the CAW600-RT automatic-weather-station （AWS）, hand anemometer and portable thermometer. The property of wind environment on the bridge site was explored through analyzing its influence factors, including mean wind speed, temperature, sunlight, topography and so on. The research results show that the Dadu River bridge is located in a deep gorge with a high altitude and a high temperature difference, where strong wind occurs nearly every afternoon and its mean wind speed is often more than 10 m/s. The causes of strong wind can be classified into two types. The first type of wind is induced by large-scale general atmospheric circulation, while the second type of wind, i.e. daily strong wind, is driven by local thermal disequilibrium, and the daily strong wind is also influenced by local terrain and time-varying sunshine. Though frequent daily strong wind has not effect on the design wind speed of the bridge, it can affect bridge durability and driving comfort to some extent.