Study On Construction Control Of The Multi-Span Continuous PC Girder Bridge With Dissymmetry Construction

The long-span bridges structure has a segmentation construction processes. Some loads of the structure as gravity, construction loads, prestress, etc, is gradually applied in the construction processes. With each construction stage possibly occurred shrinkage and creep, the boundary constraints increasing or decreasing, prestress tendons tensioning and system conversion etc, the structure geometric linear and stress states also in change. During cantilever casting of multi-span continuous prestressed concrete box girders, if the closures of the bridge using the way of dissymmetry construction, the linear control of the bridge will be more complicated.Based on the project of the Hanshou Yuanshui Bridge, the thesis mainly analyses and studies those primary factors which make influence on linear and stress of the bridge. Through establishing spatial beam-element models by BRanalysis, 3-D solid models by ANSYS and spatial beam-element models by MIDAS, combining with the practice of construction control, the thesis makes the simulation analysis about the whole construction processes, and carries out the research work from the following aspects:1. Generalized the bridge structure analysis theory and method in the process of construction control, in order to offer the theory for structure simulation analysis and establish the theory base to implement the practice of bridge engineering construction control successfully.2. Introducing the ideas and methods of establishing spatial beam-element models by BRanalysis, 3-D solid models by ANSYS.3. Calculated the internal force, deformation and status parameters of structure in every stage according to the Hanshou Yuanshui Bridge, to analyze the typical stages as cantilever casting of box girders, structure system conversion, etc; to establish the ideal finite element model with symmetry construction of the bridge and compare to the actually dissymmetry construction result of simulation calculation, to study inflence of the shrinkage and creep of concrete and dissymmetry construction on the deflection and stress etc of the continuous box girders. To find out the variation rule of deflection and stress of box girders in the segmentation construction processes.4. Based on the ralative reference works, proposed the common objective function of construction control, and the half analytic formula of sensitive factor which based on objective of construction control, and to verificate the formula by sensitivity analysis of parameters applying in the project. 5. Proposed more scientific and reasonable operation standard for the double-control technology in the process of tensioning the tendons by analyzing the sensitive degree of tension control stress for tensioning elongation of prestressed tendon.6. Selected several parameters which influence the normal stress of box girder lower margin to do sensitivity analysis, in order to seek the influence of the normal stress of box girder lower margin by later bottom plate tendon tensioning., through applying the function of MIDAS which can simulate the tensile state of prestressed tendon before grouting and making use of sensitivity analysis method.7. Finally, to identify some main parameters and determine the estimate value of every parameter by using the least square method, to offer the more reasonable states of intermediate objective or real structure in bridge construction.