基于修正断裂分析模型的混凝土劈拉强度预测

PRIDICTION OF SPLITTING TENSILE STRENGTH OF CONCRETE UPON MODIFIED FRACTURE ANALYSIS MODEL

数值分析是规避试验短板、实现理论预期的重要研究手段。该文采用细观尺度数值试验方法,对建立的基于绕晶失效模式的混凝土三维细观断裂理论分析模型进行修正。采用的混凝土数值分析模型由砂浆、界面及骨料组成,与理论分析模型保持一致。为模拟普通强度混凝土的力学行为,采用塑性损伤本构模型表征砂浆和界面的力学性能,骨料则设为弹性球体。采用自编骨料投放程序,建立了截面尺寸分别为100 mm(一级配)、150 mm(二级配)、300 mm(三级配)和450 mm(四级配)的三维模型混凝土标准立方体试件。通过开展不同界面强度条件下标准立方体试件劈裂拉伸加载数值试验,对理论分析模型进行了修正,建立了用于不同级配混凝土劈拉强度预测的半理论-半经验修正计算公式。与数值试验及物理试验结果对比表明:修正后的理论分析模型能够有效表征混凝土宏观力学性能随细观组成材料力学特性和结构特性的变化规律。该文提出的基于重叠效应和结构效应分析的理论模型修正方法,可为后续建立基于修正断裂分析模型的混凝土力学性能半理论-半经验预测公式奠定基础。

Numerical analysis is an important research method to avoid the shortcomings of experiments and to realize theoretical expectations.Based on the mesoscale numerical test method,the established intergranular failure mode-based three-dimensional meso-fracture theoretical analysis model of concrete is modified.The adopted numerical model of concrete is composed of mortar,interfaces and aggregates,which is consistent with the theoretical model.In order to simulate the mechanical behaviors of ordinary strength concrete,the plastic damage constitutive model is used to characterize the mechanical properties of mortar and interfaces,and aggregates are set as elastic spheres.A self-designed aggregate placement program is used to establish standard cubic specimens of three-dimensional model concrete with cross-sectional dimensions of 100 mm(1-graded),150 mm(2-graded),300 mm(3-graded)and 450 mm(4-graded).The theoretical model is improved by the splitting tensile loading numerical tests of standard cubic specimens under different interfacial strength conditions.A semi-theoretical and semi-empirical modified calculation formula for predicting the splitting tensile strength of different graded concrete is established.Compared with the results of numerical and physical tests,the modified theoretical model can effectively represent the variation of the macroscopic mechanical properties of concrete with the mechanical and structural properties of meso-component materials.The proposed theoretical model modification method based on overlapping effect analysis and structural effect analysis can lay a foundation for the subsequent establishment of semi-theoretical and semi-empirical prediction formula of concrete mechanical properties upon modified fracture analysis model.