The Research On Construction Control In The Incremental Launching Of Main Girder Of Cable-stayed Bridge With Steel Box Girder

This dissertation is based on the background of construction of Ji'nan Yellow River Bridge on Qingdao-Yinchuan Expressway. The construction process simulation and construction control of steel box girder bridge with incremental launching method is studied. Differed from cantilever method, the most prominent characteristic of incremental launching method is that the coordinate, supporting condition as well as the corresponding internal force and deformation of the structure are constantly changing during the construction. In response to this feature, finite element technology is utilized in this paper. This feasible method effectively realized the simulation during the process of incremental launching method. Moreover, this thesis analyzed the sensitivity of several design parameters which might have influences on internal force and deformation of structure during the construction stage. In addition, unstressed state control method was successfully adopted to modulate the line shape of the steel box girder. This method ensured that the line shape and internal force condition of the steel box girder were always be restrained in the range of design requirements during the construction stage as well as after the completion of incremental launching construction.First of all, this article summarized the origin, development, construction characteristics, and the application in steel box girder as well as the problem of this application of incremental launching method. The contents, methods and influencing factors of control of bridge construction were expounded. The line shape and stress control were established as the contents of the construction control during the incremental launching construction stage of Ji'nan Yellow River Bridge on Qingdao-Yinchuan Expressway, and give priority to line shape control, stress control is a supplement.In order to successfully implement construction control, this paper detailed the whole process and method of construction of Ji'nan Yellow River Bridge on Qingdao-Yinchuan Expressway, from the construction of incremental launching of steel box girder to the lock of the whole bridge. A finite element software MIDAS/Civil was used to calculate the internal force and deformation of steel box girder during the whole process of incremental launching construction stage. The dynamic variation of internal force, stress and deformation of girder during the construction stage were analyzed. The calculation provided a theoretical data for construction control.Several design parameters, which were likely to have impact on the internal force and deformation of girder during the construction stage were analyzed. Through the sensitivity analysis, the self-weight of the structure and some other factors were considered as main parameters, which should be concerned and amended during the construction process.Finally, based on the structure analysis and sensitivity analysis of parameters, the construction control was applied into the process of incremental launching construction of Ji'nan Yellow River Bridge on Qingdao-Yinchuan Expressway. The principle of construction control is that the non-stress condition of structure should consistent with the design condition. By adjusting and controlling the line shape of the steel box girder as well as monitoring and testing the stress of the steel box girder, the successful implementation of construction control and the carrying out of the incremental launching construction were ensured.With the combination of theoretical calculation, parameters analysis and construction monitoring, construction control of incremental launching method of steel box girder were successfully achieved, which have certain reference value for the structure analysis and construction monitoring of this type of bridge with incremental launching method.