基于细观层次的复杂加载路径下混凝土动态损伤演化模型研究

The dynamic constitutive model are the theoretical bases for the study of mass concrete under complex stress. However, relevant parameters of dynamic constitutive model for concrete based on the strain rate effect are not enough to understand the mechanism of dynamic effect in concrete, lacking mature dynamic constitutive model of concrete based on microscopic and mesoscopic levels. Literature and previous research work show that studying the variation mechanism of dynamic strength in concrete under complex loading paths from mesoscopic levels is of scientific value and significance. This study aimed to investigate the dynamic stress state, damage area, failure energy, and dynamic strength of concrete specimens under complex loading path based on the principle of least energy consumption. The effects of factors, such as pre-static load, loading rate, loading mode, and size, on the dynamic strength of concrete, variation law of dynamic strength, and evolution process of crack damage in concrete materials under complex loading paths were studied through theoretical analysis of nonlinear thermodynamics, numerical simulation, and dynamic triaxial CT test. The failure criterion of dynamic strength described by damage area and failure energy was established, dynamic strength theory under complex loading paths was proposed, and dynamic damage mechanism of concrete was revealed. This study provided a theoretical basis for the dynamic strength variation of concrete under complex loading paths . The findings might have practical significance for Seismic and explosion resistant design and healthy service of concrete structures.

混凝土动本构模型是复杂加载路径下混凝土材料动强度研究的理论基础，但基于应变率效应混凝土动态本构模型的相关参数对混凝土动态效应的机理认识不够充分，缺少成熟的基于微观、细观层面的混凝土动态本构模型。文献和本团队以往的研究工作表明，从细观角度研究复杂加载路径下混凝土动强度变化机理具有科学价值和意义，本课题拟以最小耗能原理为理论基础，对混凝土试件在复杂加载路径下的动应力状态、破坏面积、破坏能及动强度进行研究，考虑预静载、加载率、加载方式、尺寸效应因素对混凝土动强度影响，通过非线性热力学理论分析、数值模拟和动三轴CT试验三条途径研究复杂加载路径下混凝土材料的动强度变化规律和裂纹损伤演化过程，建立由破坏面积和破坏能描述损伤变量的动强度破坏准则，提出复杂加载路径下动强度理论，揭示混凝土动态损伤机理。本研究为复杂加载路径下混凝土材料动强度变化规律提供理论基础，对混凝土抗震和抗爆炸设计及健康服役有实际意义。

文献和本团队从细观角度研究复杂加载路径下混凝土动强度变化机理具有科学价值和意义，本课题以最小耗能原理为理论基础，对混凝土试件在复杂加载路径下的动应力状态、破坏面积、破坏能及动强度进行研究，考虑预静载、 加载率、加载方式、尺寸效应因素对混凝土动强度影响，通过运用非线 性热力学理论分析、数值模拟和动三轴CT试验三条途径研究复杂加载路径下混凝土材料的动强度变化规律和裂纹损伤演化过程，建立了 由破坏面积和破坏能描述损伤变量的动强度破坏准则，提出了复杂荷 载作用下动强度理论，另对CT图像中试件的破坏面积进行计算，研究混凝土试件破坏过程中外界输入能量与其内部能量之间的转化机理，以及随着破坏面积的扩大总能量和应变能的消耗情况。揭示混凝土动态损伤机理。本研究为爆炸、 地震作用下混凝土材料动强度变化规律提供理论基础，对混凝土抗 震和抗爆炸设计及健康服役有实际意义。