Cantilever Casting Of Prestressed Concrete Continuous Beam Bridge The No.0 Space Stress State Analysis

With the increase of the span of the prestressed concrete continuous girder bridges constructed by cantilever method, the strength of concrete material is much higher and the volume of the zero block is much bigger than before. The stress is so complex that the zero block often has crack in the course of constructing and running. This situation brings serious safety problem and has been widely regarded by the bridge engineer.With the Liu yang River Bridge in Changsha city as supporting engineering, first of all, the spatial entity mode of finite element is established to analyze the temperature stress field and discuss the influences of the constraint, shrinkage and prestressing force on the stress field of the zero block, subsequently the further study on the stress distribution characteristics of the zero block and the summarization of the changing regularity of the stress in some typical construction stages are conducted, in the end, the area where the cracks most likely happen is put forward, which provides scientific and effective measures for the zero block design.The research of the paper shows that the heat of hydration accumulates rapidly in the process of concrete pouring. The inner temperature of the cross clapboard is the highest because of its bigger volume, which is also the focus of the temperature controlling. The internal-external temperature difference causes crack in premature concrete, and the temperature difference or shrinkage causes biggish tensile stress near the superfluous constraints and the prestressing force can reduce the tensile stress of the zero block. The maximum principal tensile stress and the vertical shear stress which lies in prestressed reinforcement anchorage zones exceeds the limit of specifications in some typical construction stages, therefore these zones are likely to crack. There is tensile stress around the bearings of the zero block also. According to the spatial finite element analysis, some useful conclusions are obtained which can afford some references to the optimum design and crack preventing of the zero block.