中文摘要：

提出了一种适用于复杂应力状态下的双折线弹性损伤模型，对混凝土试件进行了轴向拉压细观数值模拟试验，同时探讨了复杂应力状态下混凝土损伤破坏机理。然后基于实际工程采用的混凝土细观动态参数试验实测值，利用细观数值模型对循环荷载作用下全级配大坝混凝土试件进行了弯折损伤破坏模拟。其数值计算结果与材料试验测的数据吻合较好，进一步验证了在循环动荷载作用下预静载对动弯拉强度也存在强化现象。本文轴向拉压细观数值模拟试验表明，细观界面黏结强度是控制混凝土宏观抗压强度和宏观抗拉强度的关键参数，而黏结面泊松比的大小对混凝土宏观抗压强度影响很大。这个研究结果表明，混凝土材料受拉破坏机制与剪切破坏机制在本质上可统一为受拉破坏机制。

英文摘要：

A bi-linear damage model is presented to study the mechanism of concrete fracturing under complicated stresses by numerical meso-simulations of axial tensile and compressive tests. The dynamic meso-strength and dynamic increase factor （DIF） of the mortar matrix, aggregate and their interfaces obtained by dynamic tensile tests are adopted to simulate the processes of flexural fracture of full-grade concrete specimens. The computational results agree well with the experiments, which show that static preloads also enhance the dynamic strengths under dynamic cyclical loads. This study shows that meso-interfacial strengths are key deterministic parameters to influence the compressive and tensile strengths of concrete, and the compressive strength is more strongly dependent on Poisson rates of the meso-interface than the tensile strength. This observation demonstrates that compressive and tensile mechanisms can be treated as a tensile mechanism in essence.