基于概率分析的混凝土箱梁温度梯度模式

为了建立混凝土箱梁的温度梯度模式,以位于浙江省千岛湖地区的一座大跨度连续刚构桥梁的温度场长期监测数据为基础，对箱梁的竖向最大正温差与环境气温之间的关系进行统计分析，建立依据日最高气温与日气温变化幅度估算混凝土箱梁竖向最大正温差的经验公式.根据极值统计理论提出箱梁的正温度梯度曲线，并与现行公路桥梁规范的温度梯度曲线进行比较.以实测气温、太阳辐射理论值为温度边界条件，根据二维热传导理论分析测试截面的理论温度场及分布特征.结果表明，现行规范的温度梯度曲线不能涵盖实测桥位地区50年一遇的气温条件，规范采用的温度梯度偏于不安全.按二维传热理论计算得到的理论温度场与实测值符合良好，理论分析能够模拟混凝土箱梁内部的温度分布特征.

Study on temperature gradient of concrete box girder based on probability analysis

In order to establish the temperature gradient mode of concrete box girder, the relationship between maximum vertical positive temperature difference and ambient temperature was statistically analyzed based on long-term temperature monitoring data of a long-span continuous rigid frame bridge in Qiandao Lake, Zhejiang Province. The empirical formula was established to estimate the maximum vertical positive temperature difference according to daily maximum air temperature and air temperature change. The positive temperature gradient curve was proposed by extreme value theory and was compared with that in the current china’s general code for design of highway bridges. The distribution characteristics of temperature field were analyzed by two-dimensional heat transfer theory using the measured temperatures and solar radiation as the boundary conditions. Results show that the temperature gradient curve of current china’s general code could not cover the temperature change on bridge site once in 50-year, which is not safe in bridge design. The temperature field calculated using two-dimensional heat transfer theory agrees well with the measured values, validating the proposed method.