Moving Mode Action Effects Of The Construction Of Prestressed Concrete Box Girder Continuous Bridge

This paper mainly researched the law of effect on the main bridge of Jili Yellow River Bridge during construction using movable scaffold system. Jili Yellow River Bridge is one of the important projects of the Tai—Ao Express Way, which lies between Jiyuan and Luoyang and is composed of three parts: south bridge approach, north bridge approach and the main bridge. The main bridge is 1,200 metres long with two-way separated road, and the superstructure is prestressed concrete continuous single cell box girder with constant section. Each span is 50 metres long, which was constructed with span by span method from south to north.It is essential for us to realize that during the construction of the main bridge using the movable scaffold system, the superstructure system transforms gradually and the effect of construction process on the internal force and geometrical linetype of the main bridge can't be neglected. However , the in-depth theoretical analysis on it is still deficient because of comparatively short period during witch the construction method was used and because of the lack of experience that should be cumulated. In order to research the law of effect of the different factors on the superstructure, to provide proper suggestions for the construction control of congeneric bridges, and to achieve the most possible accordance between the cpmplete and designed bridge, three aspects work was done in this paper in virture of the Jili Yellow River Bridge project.1. By periodically surveying the elevation of different control section of each span according to four construction phases during the construction of entirely bridge, a large number of valuable data were obtained which reflected the vertical deformation of the box girder with the development of construction process and provide a important foundation to the FE simulation and the further in-depth analysis. The data showed that each span has biggish vertical deformation, the deformation of each complete span was affected by the construction of successive span and, in the different construction processes, a certain torsional deformation happened during the four construction phases of each span.2. According to the trait of prestressed conrete box girder, a FEM analysis model was established using shell and 3D link elements of programme ANSYS, which provide a foundation for the research of effect on the structure of different factors such as the movement of the scaffold, death load of box girder, prestressing, bearing displacement, the change of environment and so on. The strategy and technique of establishing simulation model of the entire bridge were also presented in detail.3. A statistic of the construction loads of box girder was done in situ. According to thestatistical results and the construction sequences and applying the high-level analytical technique: death and birth of elements, a construction simulation was carried out. The result demonstrated that the internal forces and the vertical deformation of each span were affected by the construction of successive spans, especially by the adjacent one, which clearly reflected the effect of construction process. The analytical result also showed that it is the most disadvantageous stage to the superstructure when the main beam of the movable scaffold system fall down at the first span. By compared with the analytical results of two different construction methods: span by span method and full staging method, it is proved that the vertical deformation of the former is larger than that of the latter.