Research On The Long-Term Deformation And Anti-crack Of Long-span PC Continuous Box-girder Bridge

With the development of transportation, the construction techniques of long span continuous beam bridge in China have been significantly improved and the scale have been reached to the advanced level in the world. However, survey data show that with the increase of operating time, the problems such as deflection increasing exceedingly and box girder cracking appear on most of the long-span continuous beam bridges. The usability and security of bridge are under serious threat by these disease. With the the mutual coupling effect the factors that cause deflection and cracking on long span continuous beam bridge are diverse and complex. So it is necessary to deeply research the causes of diseases, explore the countermeasures to overcome deflection and cracking.In this paper, relying on China Railway 15rh Bureau of Science and technology Project of the research on the causes of prestressed concrete box girder continuous long-term deflection of Foshan Huayang Bridge and Guangdong Procincial Department of Transportation Technology Project of the design technique of long-span prestressing concrete continuous bridge for serviceability, the main factors influencing the deflection and cracking on long-span continuous beam bridges are researched from two aspects of theoretical derivation and numerical simulation. The main research contents and results reflected in the following respects:(1)Trough consulting a large number of relevant literature, the research results on long-term deflection and cracking of prestressed concrete box girder bridge are summarized, and the main factors that may cause deflection and cracking on box girder beam bridge are discussed in this paper, providing a basis for further research.(2)Taking Foshan Huayang Bridge as a calculation example, the superstructure space model of Huayang Bridge is established by using finite element software MIDAS/Civil, The influence of vertical prestressing lose, unequal settlement of pier, beam overweight, increasing pavement thickness, shrinkage and creep of concrete on this bridge are analyzed. The analysis results shows that:The more prestressing loss, the greater the main beam deflection; Unequal settlement of pier influences the linearis of middle span and side span; The increasing deflection caused by beam overweight and increasing pavement thickness can not be ignored; The specification from different country has different deflection forecast on main girder. Shrinkage and creep of concrete is one of the leading causes of long-term deflection(3)The influence of fiber concrete for main beam deflection is researched and analysised. Though calculating the finite element model with steel fiber reinforced concrete and polyacrylonitrile fiber reinforced concrete, the influence law of fiber concrete for main beam deflection is concluded. At the same time, the deflection influence effect of three kinds of scheme of fiber reinforced concrete used in different part of bridge are compared, the characteristics of each scheme are analyzed.(4)The main beam zero block model is established by using general finite element software ABAQUS. According to the sensitive characteristic of the zero block to stress, the influence of the prestressed loss stress on the zero block analysed. The stress change rule of zero block with different degree of prestress loss is concluded. The fragile parts of zero block in service stage are summed up.In this paper, the research achievements of long-term deflection of long span continuous box girder bridge and cracking factors and the specific effect can provide some useful reference for large span bridge engineering practice in the future.