混凝土箱梁温度梯度模式的地域差异性及分区研究

为了对混凝土箱梁温度梯度中温差取值的地域差异性和分区进行研究,对一混凝土箱梁桥开展长期温度场测试与有限元数值模拟,通过实测数据给出混凝土箱梁竖向温度梯度曲线形式,采用广义极值分布得到温度梯度中的温差代表值。建立有限元模型对中国34个主要城市混凝土箱梁温差进行计算,以地理、气象参数回归计算温差代表值的经验公式,在此基础上,对中国361座城市的混凝土箱梁温差代表值进行初步分区。研究结果表明：基于实测数据的混凝土箱梁竖向温度梯度曲线接近于新西兰规范推荐的"顶部5次抛物线"和"底部线性段"的形式;混凝土箱梁的顶部温差T₁和底部温差T₂分别服从参数为W（6.86,4.49,-0.42）和W（-0.32,1.46,-0.40）的Weibull分布,广东东莞地区混凝土箱梁顶、底部50年重现期的温差代表值分别为17.3℃和3.1℃;建立了以纬度l、海拔H和日温差T_V为参数的混凝土箱梁顶部温差代表值T_1,ref和底部温差代表值T_2,ref的经验公式,可以很好地反映中国混凝土箱梁温差取值的地域差异性,与已有研究成果亦可相互验证;基于经验公式,初步将中国划分为4个区域进行温差取值,4个区域T_1,ref的取值分别为18℃,20℃,23℃,29℃,T_2,ref的取值分别为4℃,5℃,6℃,7℃;提出的经验公式和温差代表值分区仅适用于100 mm沥青铺装的混凝土箱梁,研究方法和结论可为中国规范关于混凝土箱梁桥温度作用的完善提供参考。

Regional Variation and Zoning of Temperature Gradient Pattern of Concrete Box Girder

To investigate regional variation and zoning of temperature differences and temperature gradient in concrete box girders, long-term temperature field measurements of a concrete box girder bridge were conducted. The vertical temperature gradient curve of the box girder was given by the measured data. Then, a generalized extreme value distribution was applied to obtain representative values of the temperature differences. Finite element models were established to calculate the temperature differences of concrete box girders in 34 major cities in China. Geologic factors and meteorological factors were used as parameters to obtain the empirical formula of the representative values of temperature difference. Based on this, the representative temperature difference values for 361 Chinese cities were calculated and zoned preliminarily. The results show thatthe vertical temperature gradient curve of the box girder based on the measured data conforms to the form recommended by the New Zealand Code, with "5th parabola at top" and "linear distribution at bottom." The temperature difference at top (T₁)and at bottom (T₂) of the concrete box girder can be subjected to the Weibull distribution with parameters of W (6.86, 4.49, -0.42) and W (-0.32, 1.46, -0.40), respectively. The representative values of T₁ and T₂ for the concrete box girder in Dongguan, Guangdong Province are 17.3℃ and 3.1℃ for a 50-year return period, respectively. In this paper, the empirical formula of the representative values T_1,ref and T_2,ref is established with the latitude l, the altitude H, and the daily air temperature difference T_V, and can be verified by the results of existing research. The formula can fully reflect the regional variation of the temperature difference in concrete box girders in China. Based on the regional variation of the representative values of temperature difference, China can be divided initially into four zones by their temperature difference values. The values of T_1,ref in the four zones are 18℃, 20℃, 23℃, and 29℃, respectively. In addition, the values of T_{2, ref} in 4 zones are 4℃, 5℃, 6℃ and 7℃, respectively. The empirical formula and the zoning map proposed in this paper are only applicable to concrete box girder with 100 mm asphalt pavement. The method and conclusion of the research can provide reference for the improvement of China's design code regarding the temperature action of concrete box girder bridges.