低纬度地区混凝土箱梁温度梯度研究

Study of Temperature Gradient of Concrete Box Girder in Low-Altitude Region

混凝土箱梁结构的温度梯度与自然环境条件密不可分,但我国公路桥梁设计规范尚未能详细考虑不同环境条件下的温度梯度。为此,对低纬度的广东地区某连续刚构箱梁截面布置温度测点并进行了长期的监测,提取混凝土箱梁沿竖向的每日最大温差数据,分析得到了沿截面高度变化的指数和折线函数相结合的正、负温差函数。依据极值理论得到50年重现期的温度梯度标准值,并与规范规定的温度梯度函数进行了对比研究。结果表明:实测竖向温度梯度可用折线和指数函数相结合的分段函数描述;气温骤降是引起箱梁负温度梯度的主要原因,实测温差数据推得的负温度梯度值大于规范规定的负温度梯度值。

The temperature gradient of concrete box girder is closely related to the natural environment.However,the highway bridge design specifications in China have not given detailed temperature gradients that are related to specific environmental conditions.In light of this issue,a continuous rigid-frame box girder bridge in Guangdong Province(a low-altitude region)is cited as a case.The bridge has been under long-term monitoring,with temperature testing points arranged on the cross section of the box girder.The daily maximum temperature difference data measured along the depth of the concrete box girder were extracted,based on which the positive and negative temperature difference functions combining the exponential and polygonal functions that vary along the depth of the cross section were gained.In accordance with the extreme value theory,the standard temperature gradients of 50-year return period were obtained and compared with the temperature gradient functions suggested in the specifications.The results demonstrate that the measured vertical temperature gradient can be described by the piecewise function that combines the polygonal and exponential functions.Negative temperature gradients are mainly caused by abrupt temperature drop and the negative temperature gradient values derived from the measured temperature difference data are greater than the values given in the specifications.