【作者】 刘会勋；

【导师】 丁红岩；

【作者基本信息】 天津大学 ， 建筑工程技术与管理， 2009， 博士

【摘要】 早龄期混凝土材料的破坏准则和本构关系是施工期混凝土结构非线性分析和计算的基础,但是由于目前其理论研究的严重滞后,造成了早龄期混凝土结构计算分析时先进算法和粗略理论的不匹配,甚至根本找不到适合的破坏准则和本构关系可以依据,从而严重的制约了模板早拆等先进施工技术的发展和应用。因此,进行早龄期混凝土材料的破坏准则和本构关系的研究,具有着重要的实用价值和理论意义。为了给最不利条件下模板早拆施工技术研究中早龄期混凝土结构的非线性计算分析提供理论依据,进行了二向应力状态下早龄期混凝土材料的强度与变形特性试验。在试验基础上,首先建立了早龄期混凝土材料的破坏准则和初始屈服准则,然后依据二者关系建立了基于非均匀等向强化法则的后继屈服准则,最后根据这三个强度准则的特性,建立了早龄期混凝土材料的弹塑性本构关系。本文的主要研究成果如下:1、通过早龄期混凝土材料的强度试验测定了立方体抗压强度、棱柱体抗压强度、轴心抗拉强度以及静力受压弹性模量,并对测试数据进行了研究分析,得到了各强度指标在试验龄期范围的最佳数学回归方程,从而为早龄期混凝土结构计算中力学参数的选取提供了理论依据;2、在早龄期混凝土单轴受压强度与变形特性试验基础上,对比分析了早龄期混凝土和普通混凝土单轴受压应力-应变全曲线的差异,并进一步通过数学方法建立了早龄期混凝土单轴受压应力-应变标准全曲线方程,从而为早龄期混凝土结构或构件在单轴受力状态下的非线性分析提供了理论依据;3、基于二向应力状态下早龄期混凝土材料强度试验数据在八面体应力空间中的分布特点,通过回归分析和数学推导,建立了八面体应力空间的早龄期混凝土材料的破坏准则、初始屈服准则和后继屈服准则,并在破坏准则基础上进一步建立了以主应力形式表达的早龄期混凝土的二轴强度包络图,从而为早龄期混凝土材料在单轴和双轴受力状态下的强度分析提供了理论依据;4、借鉴弹塑性本构理论,根据早龄期混凝土材料的破坏包络面、初始屈服包络面以及参照面对八面体应力空间的划分状况,依据被划分区域和两个强度包络面及参照面在应力空间中的相对位置关系,分别给出了各划分区域的本构模型,进而得到了早龄期混凝土材料一般形式的弹塑性本构关系,从而为早龄期混凝土结构或构件在双轴受力状态下的非线性分析提供了理论依据。更多还原

【Abstract】 The failure criterion and constitutive relation of the early-age concrete is the basis of the nonlinear analysis on the concrete structure in the construction. However, due to the lagging theoretical research, the impreciese theory can not match the advanced algorithms in the nonlinear analysis, even there are not the ture failure criterion and constitutive relation, which will have a serious effect on the application and development of the advanced technology such as the early dismantling formwork construction. As a result, the research on the failure criterion and constitutive relation have important practical value and theoretical significance.In order to give theoretical basis for the non-linear analysis of the early-age C20 concrete structure in the most-unfavorable diathesis-based early dismantling formwork construction technology, the test of the concrete strength and deformation was carried out under the biaxial stress state. On an experimental results, firstly the failure criterion and the initial yield criterion of early-age C20 concrete materials are established, and then the subsequent yield criterion can be derived based on the non-uniform isotropic strengthening criterion, finally elastic-plastic constitutive relation is established according to the three criteria. The main research results are as follows:1. The cube compressive strength, prism compressive strength, axial tensile strength and static elastic modulus of compression can be set out in the early-age C20 concrete strength test. According to the test data, the best mathematical regression equation of the strength indicators in the test age range can be made, which will provide the theoretical basis for the mechanical parameters of the calculation.2. In the experimental basis, the difference of uniaxial compression stress-strain curve between early-age C20 concrete materials and conventional concrete materials is analyzed, and the more precise uniaxial compression stress-strain standard curve equation can be established through mathematical method, so as to provide the theoretical basis for non-linear analysis of early-age C20 concrete structures or structural members under the uniaxial state.3. According to the distribution characteristics of strength test data in the octahedral stress space, using the method of the linear fitting and mathematical derivation, the failure criterion, the initial yield criterion and the subsequent yield criterion of early-age C20 concrete materials in the octahedral stress space are established, and then the biaxial strength envelope curve of early-age C20 concrete materials in the form of principal stress is achieved on the basis of failure criterion, so as to provide the theoretical foundation for the strength analysis of the early-age C20 concrete materials under uniaxial and biaxial stress state.4. Considering the elastic-plastic constitutive theory and based on the early-age C20 concrete failure envelope, the initial yield envelope and the reference surface, octahedral stress space can be divided. Based on the location relationship in stess space according to the divided region, the two intensity envelope and the reference surface, the elastic-plastic constitutive model of the divided region is established, which the general elastic-plastic constitutive relation for early-age C20 concrete materials is made. All of this can supply the theoretical basis for non-linear analysis of early-age C20 concrete structures or structural members under the biaxial state.更多还原