Prediction Of Thermal Effects, Shrinkage And Creep Effects, And Prestress Losses In Long-Span PC Box Girder Bridge

The structural behaviors such as thermal effects, shrinkage and creep effects of thin-walled box girder bridges and the losses of prestressing are complicated problems which have not been resolved completely but needing resolved urgently in bridge engineering. Combined with the facts of bridges, the investigations are carried out to obtain structural behaviors of thin-walled box girder bridges under non-loading actions, which would bring practical values and theoretical meanings to the application of thin-walled concrete box girder in long-span bridges. In conjunction with a project of the Transport Department of Hunan province, a series of experimental and analytical research on the long-span PC bridges with thin-walled box girder, including the thermal field in box girder, the thermal effects, the shrinkage and creep effects of Box Girder Bridge, and the prestress losses, have been performed in this dissertation. The main investigations are summarized as follows (including three parts): 1.The thermal effects(1) Field measurements about the temperature distribution and the thermal response in the bridge during its construction and service stage were carried out for several times. Then a comprehensive investigation on the recorded data from different seasons was conducted. And the influence on the temperature variation of factors including the deck pavement and the height of the box girder was discussed. In addition, to estimate the temperature distribution (including positive and negative) in bridges, an analytical model based on ANSYS is described. The model takes into account several factors and very good agreement between measured and calculated temperatures was achieved. It revealed that the methods, the parameters, the boundary condition used in this dissertation are reasonable. Then on the basis of the measured and calculated temperatures, a model considering both the vertical and the transverse variation of concrete box gieder is developed.(2) Based on the temperature distribution model developed in this dissertation and ANSYS, a detailed analysis on the thermal response in the bridges is conducted. The validity of the model is tested against strain data obtained from field measurements. In addition, a comparison of the model developed in this theis with the current design specifications for thermal loads is presented. And the results revealed that to positive thermal effects, the nonlinear model with the values of design thermal loads of 20~25...