混凝土拱肋立式预制施工期温度及收缩裂缝问题研究

发布时间：2018-12-12 15:43

【摘要】：混凝土预制构件生产周期内经常会出现裂缝问题,这是一个比较普遍的现象,也是长期困扰工程技术人员的技术难题。本文以一实际工程为背景,从温度变形、收缩变形、约束以及混凝土早期受拉徐变四个方面,探究混凝土拱肋立式预制施工期温度及收缩裂缝形成原因,并由预制形式的相似性,延伸到混凝土T梁和混凝土小箱梁施工期裂缝问题的研究。在此基础上,结合混凝土结构特点提出预制构件施工期裂缝控制措施,以满足工程应用需要。本文主要研究内容如下：(1)混凝土构件立式预制施工期温度应力研究阐述混凝土温度变形裂缝产生的一般机理,给出温度问题基本方程,根据平底模立式预制构件温度应力计算公式推导出弧形底模立式预制构件温度应力计算公式,并探讨与温度应力计算相关参数的选取。(2)混凝土构件立式预制施工期收缩及徐变效应研究阐述混凝土收缩裂缝产生的一般机理,总结收缩主要形式以及收缩常用的计算模式,并总结了早期受拉徐变方面相关研究,给出混凝土早期受拉徐变一般计算方法。(3)背景工程分析结合现场施工调查情况以及拱肋裂缝特点,从温度、收缩、外约束以及施工过程四个方面对立式预制混凝土拱肋裂缝问题进行分析,根据初步分析的结果,对拱肋裂缝问题进行验算。根据立式预制混凝土拱肋温度应力计算公式,求得温度及收缩应力理论值；根据拱肋早期自约束应力计算公式以及外约束应力计算公式,求得拱肋早期温度应力。(4)混凝土拱肋立式预制施工期温度及收缩应力有限元模拟总结混凝土结构温度及收缩应力有限元模拟的一般方法,结合背景工程,通过有限元软件模拟混凝土拱肋的早期温度场、混凝土拱肋的早期温度应力以及混凝土拱肋的温度及收缩应力,并将模拟结果与理论计算值进行对比分析。(5)混凝土构件立式预制施工期裂缝控制研究从混凝土构件预制形式、底模约束以及温度作用三个方面进行了立式预制构件施工期裂缝影响研究,分析了各个因素的影响程度,并提出了相应的施工建议。
[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.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U445.57

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