The Temperature Fields Of Long-Span PC Box-Continuous Beam Bridges And Its Effects

In recent years, developing completely along with high grade highway and stereoscopic transportation in cities, bridge development has entered the unprecedented high tide period. Among them the box girder occupies important position in developments of the long-span PC beam bridge with its good section-form. But in construction and application of domestic and international bridge, some serious cracks have been discovered, which caused very terrible results, so they arouse the attention of bridge experts and researchers in the world. It has been proved by the theoretic analysis and experiment that temperature stress is the main factor that leads concrete box girder to crack. It has been proved by examples of engineering practice that temperature fields did great effect on the stress and line deformation of long-span PC continuous box girder bridges. Therefore, it is necessary to get temperature mode and its effect on the stress and the line deformation in one region of our country by theories and experiments. It can be used in the bridge design, which makes a reasonable time to construct, sprinkle concrete and control appropriate temperature on key constructing processes.Currently, the calculating theories of concrete-beam temperature fields can be divided summarily into three types:Category 1 is the method of how the hot conduct in the square distance; Category 2 is the proximate-number analytical method, such as Finite Difference Method, Finite Element Method etc.; Category 3 is a half experience and half theoretic method.On the basis of analyzing every kind of methods above, this paper will make a research from five aspects as following.1. According to the examples of engineering practice, we can build up temperature-calculating modes of box section and then calculate temperature fields of box section by measuring the boundary conditions and restricting conditions.2. By ANSYS, we can build temperature-calculating modes of P.C box girder T and then calculate the effect of temperature fields on the stress and the linedeformation.3. Adopt the spot-measure method. By measuring the temperature of temperature-feeling machine of pre depositing in the box sections, I can get the varying temperature data of different time in box sections, then make use of these temperature test datas, figure out the variety regulation of temperature distribution along the high direction in box section with the nerve network method, then I get temperature fields of box section along the high direction.4. By measuring the stress and the line deformation of control box section, I can assure the mode of temperature fields in long-span PC continuous box girder bridges and its effect on stress and the line deformation at certain time. By the temperature fields effect on stress and the line moves in different time, I can get the nonlinear relationship about temperature fields and its effect on stress and the line deformation.5. Finally, I will compare the spot measure results with the results which calculated by an analysis software ANSYS, so I can verify the temperature step-mode. Then I can further make sure the temperature mode and its effect on the stress and line deformation in one region of our country.