早龄期混凝土材料与构件力学性能试验研究

发布时间：2018-06-21 15:10

本文选题：早龄期混凝土 + 力学性能　；参考：《北京交通大学》2016年博士论文

【摘要】：混凝土早龄期性能指标是推定混凝土质量优劣的重要依据之一。早龄期混凝土力学性能不仅是影响施工期结构安全的关键因素和工程进度的制约因素,而且直接影响混凝土服役期性能及其耐久性。目前早龄期钢筋混凝土领域的研究多限于材料领域的研究,对于早龄期混凝土构件尚未形成系统研究分析。因此,研究早龄期混凝土材料与构件的力学性能及变化规律有重要的理论意义与应用价值。本文完成的主要研究工作及创新成果如下:(1)完成了龄期为0.5天、1天、3天、7天、14天、28天和90天的混凝土试块立方体抗压强度、轴心抗压强度、劈裂强度、静力弹性模量、单轴受压全曲线和粘结滑移试验研究,对试验结果进行分析,得出混凝土"三强度一模量"随龄期的增长规律及计算方法,在试验基础上建立了早龄期混凝土单轴本构关系和粘结滑移本构关系曲线。(2)完成了 1天、3天、7天、28天早龄期C40钢筋混凝土梁试验,对不同龄期试件在分级荷载作用下的典型破坏形态进行深入分析,研究了荷载、龄期等因素对构件承载能力、变形性能及前期受荷对后期承载力的影响,提出了早龄期钢筋混凝土梁正截面抗弯承载力、极限承载力计算公式。利用ABAQUS软件模拟了龄期为3天、7天、28天钢筋和混凝土的应力、变形图,并结合配筋率、剪跨比进行了有限元扩展分析。(3)完成了1天、3天、7天、28天龄期C40钢筋混凝土柱偏心加载试验,测量了试验构件的挠度、轴向变形、转动变形及截面应变,并绘制了在单调荷载作用下柱的裂缝分布图,全面分析了荷载-应变曲线及其特征,提出了早龄期钢筋混凝土偏心受压柱的正截面开裂荷载计算公式,并依据修正平截面假定法,提出一种早龄期偏心受压承载力的实用计算方法,其计算值与试验数据吻合良好。在试验基础上,运用有限元软件ABAQUS模拟得到的3天、7天、28天的极限荷载与试验荷载较为吻合,并结合配筋率、偏心距进行了有限元扩展分析。(4)根据C40混凝土早龄期性能试验,研究了原材料、混凝土配合比等对混凝土的密实度和抗裂性的影响,并通过混凝土早龄期碳化深度、自由收缩、限制膨胀率、平板约束等试验,分析和验证了所选原材料、配合比对混凝土耐久性的影响,建立了早龄期混凝土高耐久性的技术控制指标。本文通过系统的试验研究,提出了 C40早龄期混凝土的抗压强度、劈拉强度、弹性模量和单轴受压全曲线随龄期的发展规律,推导出合理的受压本构关系模型;对早龄期钢筋混凝土受弯、受压构件的受荷特性和破坏机理进行研究分析,提出了早龄期钢筋混凝土构件极限承载力计算公式;结合早龄期性能特点,研究原材料选择、混凝土配合比对混凝土高耐久性的影响,提出了控制混凝土密实度、抗裂性的技术指标。
[Abstract]:The early age performance index of concrete is one of the important bases to estimate the quality of concrete. The mechanical properties of early age concrete are not only the key factors of structural safety during construction period and the restriction factor of project progress, but also directly affect the performance and durability of concrete service life. At present, most of the researches in the field of early age reinforced concrete are limited to those in the field of materials, but there is no systematic research and analysis on early age concrete members. Therefore, it is of great theoretical significance and practical value to study the mechanical properties and variation law of early age concrete materials and members. The main research work and innovative results of this paper are as follows: (1) the cube compressive strength, axial compressive strength, splitting strength, static elastic modulus of concrete test blocks with the age of 0.5 days / 1 day / 3 days / 7 days / 14 days / 28 days and 90 days are completed. The experimental study of uniaxial compression curve and bond-slip test is carried out. The experimental results are analyzed, and the increasing law and calculation method of concrete "three strength and one modulus" with age are obtained. The uniaxial constitutive relation and bond-slip constitutive relation curve of early age concrete were established on the basis of the test. In this paper, the typical failure patterns of specimens of different ages under graded loads are analyzed in depth. The effects of load, age and other factors on the bearing capacity, deformation performance and early loading on the later bearing capacity of the members are studied. The formulas of flexural bearing capacity and ultimate bearing capacity of early age reinforced concrete beams are presented. By using Abaqus software, the stress and deformation diagram of steel bar and concrete with the age of 3 days, 7 days and 28 days were simulated, and the reinforcement ratio was combined. The shear span ratio was analyzed by finite element method. (3) the eccentric loading test of C40 reinforced concrete column at 28 days of age was completed in 1 day, 3 days, 7 days and 28 days. The deflection, axial deformation, rotational deformation and cross section strain of the test members were measured. The crack distribution diagram of columns under monotonic load is drawn, the load-strain curve and its characteristics are analyzed comprehensively, and the formula for calculating the normal section cracking load of eccentric compression columns of early age reinforced concrete is put forward. On the basis of the modified plane section assumption method, a practical method for calculating the eccentricity compressive capacity of early age is proposed. The calculated values are in good agreement with the experimental data. On the basis of the test, the limit load of 3 days and 7 days and 28 days obtained by using the finite element software Abaqus is in good agreement with the test load. Combining with the reinforcement ratio and eccentricity, the finite element expansion analysis is carried out. (4) according to the early age performance test of C40 concrete, the finite element expansion analysis is carried out on the basis of the reinforcement ratio and eccentricity. The effects of raw materials and concrete mix ratio on the compactness and crack resistance of concrete are studied. The selected raw materials are analyzed and verified through the tests of early age carbonation depth, free shrinkage, limited expansion rate, plate restraint, etc. The technical control index of high durability of early age concrete is established based on the effect of mix ratio on durability of concrete. In this paper, through systematic test and study, the compressive strength, splitting tensile strength, elastic modulus and uniaxial compressive full curve of C40 early age concrete are put forward, and the reasonable constitutive relation model of compression is deduced. In this paper, the loading characteristics and failure mechanism of early age reinforced concrete members under bending and compression are studied and analyzed, and the formula for calculating ultimate bearing capacity of early age reinforced concrete members is put forward, and the selection of raw materials is studied according to the characteristics of early age behavior. The influence of concrete mix ratio on the high durability of concrete is discussed, and the technical index of controlling the compactness and crack resistance of concrete is put forward.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU528

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