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.