Research On The Time-dependent Temperature Field And Its Effect Of The Prestressed Concrete Box-Girder

In recent years, with the rapid development of transportation industry, bridge construction has entered a unprecedented high-speed development period. In the process of bridge structure designation, rational selection of section is particularly important. Box girder, with its excellent characteristic, has became the first choice of multitudinous section forms of long-span prestressed concrete bridge. However, different extent cracks have been discovered in the construction and application of some domestic and international concrete bridges. Many studies had shown that the thermal effect on the structure was the main factor which induced these cracks.,but it was not fully considered in the designation of bridges.In this paper, based on a long-span PC continuous rigid frame bridge, the time-dependent distribution rule of hydration heat temperature field about concrete 0# block and sunshine temperature field about concrete box girder will be analyzed respectively, afterwards, the temperature effect to bridge can be researched. Through theoretical calculation, the least favorable influence about occurrence time and condition to bridge which is caused by temperature effect can be predicted, and then, in order to guide the construction, the reasonable temperature control measures can be came up with. The main research contents include the following two aspects:(1)According to the transient temperature heat transfer theory, on the basis of the boundary conditions and the practical constraints, considering the time-dependent influence of thermal characteristics of materials at the same time, in this paper, the time-dependent hydration heat temperature field and its effect of box girder 0# block is researched, in the meantime, under the time-dependent convective heat transfer condition, the hydration heat temperature field distribution of concrete box girder is aslo analyzed. Through the comparison between measured and analyzed data, the occurrence time of temperature peak and temperature differentials peak will be determined in the depositing process of box girder 0# block, and then, the response of temperature effect in the depositing process of box girder 0# block can be obtained.(2)Under the monitor of sunshine temperature field of concrete box girder, the time-dependent temperature distribution rule will be reserched on the response of sunshine. Comparing the relevant stipulations about the temperature load in domestic and international codes, the temperature grandient model of concrete box girder can be established. Through the comparison between measured and analyzed data, the occurrence time of the least favorable temperature grandient model of concrete box girder will be ascertained, and then, the influence about stress and deflection to bridge what is caused by the least favorable temperature grandient model can be analyzed.