基于多尺度理论的混凝土多轴力学性能尺寸效应研究

Concrete structure is one of the most widely used structures in the civil engineering. The size effect on mechanical properties of concrete material is directly related to the safety of the structure. Scholars have performed a lot of research on the size effect of concrete behavior under uniaxial loading. But in the actual structures, the concrete is under multiaxial loading. Therefore, the real understanding of size effect of concrete under multiaxial loading is quite necessary. Based on the multiscale theory, this project will perform macroscopical and mesoscopical research on the size effect of concrete mechanical peoperties under multiaxial loading. Based on the experimental study, numerical simulation and theoretical analysis, this project will obtain the mechanical performances and the failure mechanism of concrete under multianxial loading. The size effect on the concrete multiaxial behavior will be determined, and the mechanism of the size effect will be revealed. Then, the mesoscopic numerical analysis models of homogeneous and heterogeneous concrete material will be established in combination with elastic brittle constitutive and both elastic brittle and plastic constitutive model for concrete mesoscopic elements. Also, the relationship between the bonding interface and concrete mechanical behavior will be established based on the mesoscopic numerical simulation and experiment result. Furthermore, the size effect law of multiaxial behavior of concrete will be proposed in this research. Therefore, the investigation on the size effect on the multiaxial behavior has the important theory significance and engineering value.

混凝土结构是我国土木工程中应用极为广泛的结构型式之一，其力学性能的尺寸效应直接关系到结构的安全。目前有关研究大多集中在单轴荷载作用下混凝土受压与受拉性能的尺寸效应，而由于实际结构中混凝土的受力状态通常是多维荷载耦合作用，因此急待发展混凝土多轴力学性能尺寸效应的理论与方法。为此，本项目结合多尺度理论，拟在宏观和细观层次上对混凝土多轴力学性能尺寸效应开展研究，主要内容有：1）混凝土多轴力学性能尺寸效应的演变规律和调控行为，试件受力破坏全过程分析；2）混凝土力学性能尺寸效应机理与建模；3）混凝土多轴力学性能细观数值分析有限元模型，包括：黏结界面层力学性能参数与混凝土宏观力学性能的关系，本构关系和材料均质性对混凝土力学性能数值分析影响；4）混凝土多轴力学性能尺寸效应数值模拟分析。通过这些研究提出适用范围较广的混凝土多轴力学性能尺寸效应律，为理论研究和工程应用提供重要参考和依据。

混凝土结构是我国土木工程中应用极为广泛的结构型式之一，其力学性能的尺寸效应直接取决于混凝土材料的尺寸效应。我国现行设计规范中混凝土结构的计算公式多是根据缩尺模型结果得到的经验或半经验公式。这些计算公式在实际大型结构中的适用性如何，需要对混凝土材料力学性能的尺寸效应进行系统研究。目前混凝土材料力学性能尺寸效应研究多集中在单轴荷载作用下的尺寸效应，关于混凝土多轴力学性能尺寸效应的研究尚不充分。本项目以混凝土多轴力学性能的尺寸效应为研究对象，在宏观和细观层次上开展研究，基于系统的试验研究、数值模拟和理论分析，掌握复杂受力状态下混凝土受力变形性能，确定混凝土多轴力学性能的尺寸效应，揭示尺寸效应的机理，建立混凝土多轴力学性能细观数值分析模型，反映混凝土细观组成结构与宏观力学性能间关系，提出混凝土多轴力学性能尺寸效应律，为理论研究和工程应用提供参考和依据。