大尺寸钢箱梁温湿度场分析

Analysis of Temperature and Humidity Field of Large-Size Steel Box Girder

为了解钢箱梁内部温度场与湿度场变化规律,以南沙大桥(原虎门二桥)工程坭洲水道桥钢箱梁为背景进行研究。考虑钢箱梁受太阳辐射、外环境气流、内部输送干燥空气(相对湿度45%)等影响,采用CFD数值模拟对昼夜不同区间下其内部温、湿度场进行分析,并与现场实测对比验证。结果表明:白昼恒温区间(14:00~17:00),钢箱梁内温度实测值与模拟值最大误差为4.1%;跨中横隔板之间相对湿度最低,通入45%干燥空气可有效避免钢箱梁腐蚀;夜晚降温区间(17:00~20:00),钢箱梁内温度实测值与模拟值最大误差为3.7%,横隔板顶部温度降幅较小,底部钢板快速降温至最低;持续通入45%的干燥空气,钢箱梁内相对湿度大于55%的区域呈跨中向两侧、自底向上扩散趋势,U肋近壁面相对湿度最高(64.7%),腐蚀风险增大。

The Nizhou Waterway Bridge of Nansha Bridge(the former Second Humen Bridge)is used as a case to study the variation law of inner temperature and humidity field of the steel box girder.The influential factors considered include solar radiation,ambient air flow and dry air conveyed inside the steel box girder(with relative humidity of 45%).The CFD numerical simulation is used to analyze the temperature and humidity field in different time intervals during day and night,and the calculated data were compared with the measured data for verification.The results show that in the time interval of 14:00-17:00,the maximum error between the measured and simulated temperatures inside the steel box girder is 4.1%.The relative humidity between the midspan diaphragms is the lowest.Conveying dry air with relative humidity of 45%can effectively prevent the corrosion of steel box girder.In the temperature-dropping time interval of 17:00-20:00,the maximum error between the measured and simulated temperatures inside the steel box girder is 3.7%,the temperature dropping degree of the top of the diaphragm is small,and the temperature in the base steel plate rapidly drops to the lowest value.Keeping conveying the dry air with relative humidity of 45%,the regions inside the steel box girder with relative humidity exceeding 55%tend to disperse from midspan to two edges of the steel box girder and from the bottom to the top.The maximum relative humidity(64.7%)occurs in the part of U-rib that is close to the box wall,where the corrosion risk is also higher.