【作者】 陈萌；

【导师】 彭少民； 刘立新；

【作者基本信息】 武汉理工大学 ， 结构工程， 2006， 博士

【摘要】 混凝土结构的收缩裂缝是学术界和工程应用中长期关注的重要课题。本文从制约其发展的视角，针对混凝土收缩变形的大小，混凝土力学行为，以及混凝土变形的约束程度等方面展开了试验研究及理论分析，从而深入地认识收缩裂缝的发展机理，并在此基础上，结合混凝土结构的特点提出有效的裂缝控制措施，以满足工程应用需要。 1．本文对28个素混凝土标准收缩构件进行了为期360d龄期的干缩变形检测，详细地分析了混凝土龄期、混凝土28d立方体抗压强度、构件所处的环境条件以及构件尺度等因素对自由干燥收缩的影响。从结构的应用出发，以混凝土28d立方体抗压强度作为一综合变量，观察、研究混凝土各个组分对收缩的影响；对于构件所处的环境条件，不仅考虑了相对湿度对自由干缩的影响，也考虑了温度对自由于缩的影响；并以构件的理论厚度来反映构件尺寸对混凝土自由干缩的影响。在标准条件下，通过对67组试验数据的回归分析，提出了自由干燥收缩的基本方程。在此基础上，改变构件所处的环境条件(温度及湿度)和构件尺寸，依据试验数据并参考已有试验资料，确定了环境中的温湿度影响系数及构件尺寸影响系数，采用多系数累积法提出了非标准条件下混凝土的自由干燥收缩估算公式，公式的计算值与130组实测干燥收缩应变值吻合良好。公式中混凝土龄期、混凝土抗压强度、环境温湿度影响系数和构件尺寸影响系数具有连续性、运算简便的特点，可在工程中推广应用。 2．将本文自由干缩估算公式、现行ACI209收缩公式和文献[1]收缩公式的计算值与实测收缩应变值进行了比较，结果表明，本文自由干缩估算公式与实测结果接近，计算精度高；此外，为了验证该式在工程应用中的适用性，将广东省洛溪大桥混凝土的收缩试验结果与本文所提出公式的计算结果进行了比较，结果表明，该式不仅可用于洛溪大桥非泵送混凝土自由干缩应变的估算，而且修正后的公式也可用于洛溪大桥泵送混凝土自由干缩应变的估算。由此，本文自由干缩估算公式反映出了混凝土自由干燥收缩随龄期、混凝更多还原

【Abstract】 The shrinkage cracking of concrete is an important problem in the academic circles and structure engineering. From the point of restraint for the shrinkage cracking, the experimental and theoretic studies are further conducted on the three basic factors (the shrinkage strains of concrete, the mechanical properties of concrete, and the degree of restraint for concrete). So, the mechanism of the shrinkage cracking is deeply studied, and the effective control measures of the shrinkage cracking for concrete structure are supposed to reply the need of the engineering.1. The drying shrinkage strains of 28 plain concrete test specimens are measured on series 360 days. The main factors (the age, the compressive strength, the environmental condition and the dimension of specimen) of shrinkage for concrete are analyzed in detail. From the point of applicability, the 28-day compressive strength for concrete is regarded as a comprehensive variable, the changes of temperature and relative humidity are all considered in the environmental condition, and the theoretic thickness of specimen is also considered. Based on 67 experimental strains, considering the influence of the concrete age and the compressive strength, the basic formula of free drying shrinkage for concrete is gained under standard condition by aggression analysis; Based on the basic formula of free drying shrinkage for concrete, the multi-coefficient formula of free drying shrinkage for concrete under non-standard condition is gained by multi-coefficient superposition method. In the formula, the temperature-relative humidity coefficient and the dimension coefficient are all considered. The calculation strains of the multi-coefficient formula are well identical with the 130 experimental strains. The above coefficients in the formula are simply, and change continually.更多还原