Influence of Boundary Conditions on the Three-Dimensional Temperature Field of a Box Girder in the Natural Environment: A Case Study

The inhomogeneous distribution of temperature in bridges causes stresses and strains inside the structure, thus affecting the safety and durability of bridges. Therefore, the study of temperature action in bridge structures is crucial; boundary conditions of the temperature field are critical to study them. In this study, the calculation method of the boundary conditions for the three-dimensional temperature field of box girders in the natural environment is investigated by taking box girders as the object, which integrates the solar radiation, environmental radiation, structural shading effect, and convective heat transfer between the inner and outer surfaces of box girders. The effects of the atmospheric transparency coefficient and concrete short-wave absorptivity on the temperature field distribution of box girders were also investigated. It is shown that the calculation results obtained by the method in this study are in good agreement with the measured results, and the method can effectively simulate the three-dimensional temperature field of the box girder. The atmospheric transparency coefficient and the short-wave absorptivity of concrete have a significant effect on the temperature field distribution of box girders, and materials with lower short-wave absorptivity can be used in the design of box girders to reduce the structural temperature.