The Full Framing Cast-in-place Prestressed Concrete Continuous Box Girder Bridge Of Cracking Analysis And Countermeasures

At present, our country bridge enterprise development is rapid, has made remarkable achievements. The application of prestressed concrete box girder bridge is more, also more common box girder bridge cracking phenomenon. At home and abroad have done a lot of research on box girder cracking mechanism, but progress is slow, did not form a system theory system. At this point, the cracking of box girder to explore is particularly important.This thesis has researched the full framing cast-in-place prestressed concrete continuous box girder bridge, using the finite element software to build models to mainly simulate the impact of the uneven subsidence of the shoring, temperature gradient, the loss of prestress on the stress state of the concrete box girder and bas put forward the solution to the cracking of the concrete. The main contents are as follows:1,This thesis has expounded the research background and research significance,summarized the development of the cracking and influencing factors of continuous box girder bridge and introduced the maintenance method of box girder bridge after cracking;2, This thesis has used the finite element software for modeling and analysis, the analysis of the mechanism of the cracking of box girder and the in-depth study of the main causes of cracking. For methods and errors of the construction cause the uneven settlement, changes of the temperature and the loss of prestress, this thesis has analyzed the mechanism of the cracking of the box girder, the change law of the stress caused by the subsidence of the whole across and local shoring, the change law of the stress of the box girder floor under the influence of the temperature gradient and the change law of the stress of the box girder floor under the influence of the loss of prestress;3, Having analyzing the causes of cracking of the box girder, this thesis has put forward to use the external prestress to enforce, and through the contrast of the stress before and after the enforcement, it is concluded that prestressed reinforcement is effective to decrease the tensile stress in the bottom of moderators. This thesis has, in brief, summarized the repair methods of the concrete and the several anti-cracking measures in construction of the framing cast-in-place bridge.