.64 M Simply Supported Slotted Box Girder Of The Temperature Field And Effect

It is known that temperature stresses are comparable to that induced by the dead or vehicle load. As one of the most important factors that lead to the cracks in bridges during construction or operation period, temperature effects may deteriorate the safety, durability and adaptability of the bridges. However, owing to the complexity of thermal effects, the current theory and computational methods for the problem are not fully developed. In practice, designers are often proceeding with over-simplified methods to predict the thermal effects, which may result in insufficient accuracy. In this thesis, the temperature effect is classified into three categories:material, climatic and artificial effects. Then, a wide variety of thermo-mechanical characteristics of the 64m-simply-supported channel-box girder was studied. The main works were as follows:1. Studies on computational methods for the 3-D thermal stresses in concrete bridges were presented. Based on the theory of thermoelasticity and an integration property of thermal stresses, a general method of computing the 3-D thermal stresses was developed and simplified. By this method, the 3-D problem was transformed into a 2-D one, where the coupling between different stress components was taken into account, so it can improve the accuracy of the analysis, while the computing works are not increased.2. A simulation analysis of the temperature field and early thermal stress was carried out during the casting of the channel-box girder, considering the concrete's time-varying characteristics in the computation:shrinkage+creep, the elastic modulus increasing with time and also the tensile strength. Then, various parameters influencing temperature field, and the corresponding measures of controlling the temperature cracks were put forward.3. Based on solar physics, heat transfer theory and so on, the mechanism of heat transfer between concrete bridges and their surroundings was studied. The boundary conditions of heat transfer in concrete bridges are defined. Then, an in-depth analysis of the temperature field and thermal stress of the bridge was conducted, meanwhile, the effect of the solar radiation intensity, ballast thickness were also studied.4. Some appropriate assumptions were made to simplify the problem, which is the temperature effect on the bridge, generated by the passing tankers, every assumption was favorable for the problem. Then, a preliminary exploring research of the temperature field and thermal stress distribution in the channel-box girder, caused by the moving radiation heat load, was finally carried out.