Study On The Construction Phase Of The Temperature And Shrinkage Crack Problem Of Vertical Precast Concrete Arch

Cracks often occur in the precast concrete production cycle, which is a relatively common phenomenon, but also is long-standing technical challenges for engineering and technical personnels. This paper is based on a practical project and explore vertical precast concrete arch rib construction of temperature and shrinkage cracks causes from temperature deformation, shrinkage, restraint and early concrete tensile creep four areas.By the similarity of the form of prefabricated, this paper extends to the study of the cracks of the construction period of concrete T beams and small concrete box girder. On this basis, combined with the structural characteristics of precast concrete, crack control measures are made to meet the engineering needs. This paper focuses on the following aspects were discussed:(1) The study of thermal stress of the vertical precast concrete elementsThis section discusses the deformation mechanism of the temperature cracks of the concrete, the basic equation of temperature problems is given. Derived prefabricated vertical curved bottom mold temperature stress is calculated based on flat vertical precast mold temperature stress formula, and also explore the calculation select parameters of temperature-related stress.(2) The study of shrinkage and creep effect of the vertical precast concrete elementsThis section discusses the general mechanism of concrete shrinkage cracks, summarizes the main form of shrinkage and shrinkage common computing model, and summarizes the research of earlier tensile creep aspect, the early concrete tensile creep General calculation methods is given.(3) The analysis of the background engineeringCombined with the field of investigation and fracture characteristics of the rib,This section analysis the problem of vertical precast concrete arch rib fracture from the temperature, shrinkage, four external constraints.According to the results of a preliminary analysis of arch rib fracture problem checking. According vertical precast concrete Rib temperature stress calculation formulas determined temperature and shrinkage stress theoretical value; formulas and external constraint stress is calculated based on self-restraint stress early ribs, and seek early temperature stress of ribs.(4) The study of the finite element simulation of the vertical precast concrete arch ribThis section discusses the general methods finite element simulation of concrete structures of temperature and shrinkage stress, combined with the background of engineering, finite element software temperature and shrinkage stress simulation of early temperature field in concrete rib, early temperature stress of concrete and concrete rib rib, and simulation results with theoretical calculations were analyzed.(5) The study of the control of cracks of vertical precast concrete elementsCarried out the construction of prefabricated vertical crack impact study analyzes the impact of each factor, and the corresponding recommendations from precast concrete construction form member, the bottom mold temperature constraints and the role of the three aspects.