Research Of Temperature Field & Temperature Stress Of Concrete Box Girder Caused By The Solar Radiation

Temperature effects that arise in bridges exposed to the environmental variables are not easily estimated, and often considered in a simplified way. It is verified that many bridge accidents were caused by temperature effects which should have be took into account carefully, now the design codes of different country on temperature load in concrete box girder have different provisions. The temperature field and temperature stress in concrete box girder bridges that caused by the solar radiation are studied in this thesis.The effect of solar radiation on temperature field in concrete box girder is researched in detail in the thesis which considers that the solar radiation is made up of three component: beam radiation, diffuse radiation and solar radiation diffusely reflected from the ground. The shadow effect of cantilever wing on web is also advised in this thesis. Some work and achievements in the research as follow:1. Based on the measurements of temperature field in shuifumiao bridge of Tan-Shao Expressway in Hunan province, the curve of vertical difference in temperature is obtained with the way of curve fit.2. Different method is used for back-calculating the thermodynamics parameter.3. According to the thermal conduct theory and Finite Element Method(FEM), the analytical model in two-dimension is build, loaded and solved with the help of macro file compiled in APDL and FEM software ANSYS. The result is compared with the data obtained in site measurements.4. The temperature stress in box girder is calculated in two-dimension model and three-dimension model respectively, two results are compared each other too.5. Parametric studies are conducting in order to find the influence of various parameters such as cantilever wing length, web depth and orientation of bridge axis on the temperature field and temperature stress. The curse between maximal horizontal difference in temperature and (web depth/cantilever wing length) is made, which may provide reference in design.Both test and analytical result show that: the temperature distribution in concrete box girder section caused by the solar radiation is nonlinear, the curse of vertical difference in temperature obtained in the way of curse fit can be expressedas exponential function as Ty =23e-6y and the linear difference in temperature 2癈 at the range of 20cm to the bottom slab. The tensile stress resulting from nonlinear difference in temperature in web is strong, so the designer should pay attention to the response of temperature effect in order to protect the concrete from cracking in design.