混凝土拱肋立式預(yù)制施工期溫度及收縮裂縫問(wèn)題研究
[Abstract]:Cracks often occur in the production cycle of concrete prefabricated components, which is a relatively common phenomenon and a technical problem that has plagued engineers and technicians for a long time. Taking a practical project as the background, this paper probes into the reasons for the temperature and shrinkage cracks of concrete arch rib during the construction period from four aspects: temperature deformation, shrinkage deformation, restraint and early tensile creep of concrete. From the similarity of prefabricated form, it extends to the crack problem of concrete T-beam and concrete box girder during the construction period. On this basis, combined with the characteristics of concrete structure, the crack control measures of prefabricated members during construction period are put forward to meet the needs of engineering application. The main contents of this paper are as follows: (1) the temperature stress of concrete members during vertical precast construction is studied. The general mechanism of temperature deformation cracks in concrete is expounded, and the basic equation of temperature problem is given. According to the calculation formula of temperature stress of vertical prefabricated member with flat bottom die, the formula of calculating temperature stress of vertical prefabricated member with arc bottom die is derived. The selection of parameters related to the calculation of temperature stress is discussed. (2) the shrinkage and creep effect of concrete members during vertical prefabrication is studied and the general mechanism of concrete shrinkage cracks is discussed. This paper summarizes the main forms of shrinkage and the commonly used calculation models of shrinkage, and summarizes the related studies on early tension-creep. The general calculation method of early tensile creep of concrete is given. (3) the background engineering analysis combined with the on-site construction investigation and the characteristics of arch rib cracks, from the temperature, shrinkage, Four aspects of external restraint and construction process of precast concrete arch ribbed cracks are analyzed. According to the results of preliminary analysis, the arch rib cracks are checked and calculated. According to the formula of temperature stress of vertical precast concrete arch rib, the theoretical values of temperature and shrinkage stress are obtained. According to the calculation formula of early self-restraint stress and external constraint stress of arch rib, The temperature and shrinkage stress of concrete arch rib during the prefabrication period are obtained. (4) the finite element simulation of temperature and shrinkage stress of concrete arch rib during the prefabricated construction period is summarized. The general method of finite element simulation of temperature and shrinkage stress of concrete structure is summarized and combined with the background engineering. The early temperature field of concrete arch rib, the early temperature stress of concrete arch rib and the temperature and shrinkage stress of concrete arch rib are simulated by finite element software. The results of simulation and theoretical calculation are compared and analyzed. (5) the crack control of concrete members during vertical precast construction is studied from the precast form of concrete members. In this paper, the influence of vertical prefabricated members on crack during construction is studied from three aspects: bottom formwork constraint and temperature action. The influence degree of each factor is analyzed, and corresponding construction suggestions are put forward.
【學(xué)位授予單位】:東南大學(xué)
【學(xué)位級(jí)別】:碩士
【學(xué)位授予年份】:2015
【分類號(hào)】:U445.57
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