Analysis Of Girder Fatigue Performance And Long-term Deflection Prediction Research Of Long-term Deflection For A Large-span Continuous Rigid Frame Bridge

With the rapid development of transportation industry in our country, the construction technologies of the large-span prestressed concrete bridges have been thoroughly developed. This kind of bridges is economic, comfort for driving and easy maintenance so that they are widely used. However, in the service period, the various forms of diseases of bridge structures have seriously affected the normal use property, including the inclined cracks in the web plates of the main beams and the excessive deflection at the mid-span. To this end, Xiangjiang Large Bridge on the Xiangfu Load of Changsha city in china is taken as an engineering example. The main works are as follows:(1) The development history of rigid frame-continuous combination system bridges is concluded. The advantages and shortcomings of this kind of bridges are addressed.(2) By comparing the concrete fatigue calculation rules of different countries, the characteristics of the standard concrete fatigue calculation steps are summarized. The finite element model of a bridge is established. The fatigue calculations for the normal section of main girder are completed by using the different country codes. It is found that the result by our country codes is conservative by comparison to the BSEN model and the specifications for CEB-FIR(3) Using the special finite element analysis software Midas/Civil for bridges, the influences of the loss of the longitudinal prestresses, the changes of structural temperature, the decrease of the structural stiffness, creep and shrinkage on the long-term deflection effects are systematically investigated. The results show that the loss of the longitudinal prestresses is the uppermost factor. The effect of the prestresses loss in the roof plate is greater than the floor plate. In addition, The concrete shrinkage and creep have also a large influence on the long-term deformation. Moreover, the structural stiffness loss has a limited effect on the long-term deformation. The variation of structural temperature has a small effect.(4) According to the analysis results in this work, the treatments for the prevention and control of the long-term deformation of the prestressed concrete continuous rigid frame bridges in the different periods from design, construction to service are proposed.