Research On Temperature Monitoring And Crack Control Of Heavy PC Box Girder On The Sea

The heavy PC box girder is widely used in sea-crossing bridge. Because of atrocious marine environment, the problem of the crack control of the concrete temperature is patently paramount in the aspects of ensuring the durability and safety for the sea-crossing bridge. Thus, engineers think much of this case tremendously. It is premise of controlling temperature cracks efficiently to predict and evaluate temperature fields of the heavy PC box girder hydration heat accurately.In this paper, based on the theoretical analysis of finite element and the project of the HangZhou Bay Sea-crossing Bridge, the hydration heat temperature fields of 70m PC box girders and the marine wet joints on the pier tops are studied by means of three tests under different conditions, which are pertinent to normal maintenance when the air temperature is low in winter and high in summer.On the basis of the full-scale testing, the distribution of hydration heat temperature in the cross-section of concrete box girder is obtained, and the rule that the temperature changes with time is presented The analysis is discussed, which is based on practically monitored data and the changes of temperature between the inside and outside of concrete ,The 70m PC box girder is characterized by high strength concrete and huge bulk. The temperature cracks are easily induced while the hydration heat temperature is excessively high. Consequently, the life of the girder will be shortened if the temperature cracks cannot be prevented from occurring. Therefore, it is important to monitor the real hydration heat temperature on every key point of the 70m girder after its concrete being cast and to study the distribution of hydration heat temperature field, the rule of the temperature changing with time. Furthermore, by analysis, the parts where thermal cracks easily emerge are worked out, and the effective measures to control the temperature cracks are proposed.Meanwhile, by the application of finite element software ANSYS, three-dimensional models for the end segment and for the typical segment of the 70m box girder are established. The rule of hydration heat on high performance marine durability concrete is analyzed, the cement hydration action is simulated and the temperature fields in the box girder's cross-section on real time are figured out. By comparing the theory results with the real monitored data, the feasibility about the analytical method of ANSYS is discussed.Finally, by means of analysis and summarizing, some measures of temperature control and crack-resistant for 70m PC box girder are advised. The application in the project...