Abstract A new set of constitutive models named TsingHua University Concrete 2D (THUC2) is developed for use in ABAQUS. THUC2 has reduced mesh sensitivity and is based on the decoupling assumption and the fixed-angle crack assumption in order to consider the pinching effect, confinement, strength degradation, and shear softening of concrete. In the developed biaxial reinforced concrete models, the uniaxial model is first established, and the biaxial model is subsequently assembled from the uniaxial model. First, the proposed uniaxial constitutive model of concrete is reported. The mesh sensitivity of the model is reduced by adjusting the descending branch of the concrete model based on mesh size. Second, a total of five biaxial constitutive models of concrete are reported to cover a wide range of simulation requirements in engineering design. Third, the numerical implementation of the proposed concrete model in both ABAQUS implicit and explicit solvers is discussed. Subsequently, the modified two-way fixed angle crack model is validated by monotonic and hysteretic panel tests. The FE model exhibits little mesh sensitivity when the element number increased from 4 to 400. The developed model accurately predicts the pinching effect and the softening effect of the panels. Finally, previous tests on two nuclear containment vessels under lateral loads are simulated, and the modified two-way fixed angle crack model demonstrates adequate accuracy in terms of predicting the initial stiffness, ultimate capacity, and pinching effect. The proposed subroutine package for simulating RC members includes the dominant mechanical behaviors of concrete and can be adopted for high-efficiency simulation of RC shear wall structures.

中文翻译：

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具有降低网格敏感性的隐式和显式求解器的双轴钢筋混凝土本构模型

摘要 开发了一套名为清华大学混凝土二维 (THUC2) 的新本构模型，用于 ABAQUS。THUC2 降低了网格敏感性，基于解耦假设和固定角度裂缝假设，以考虑混凝土的挤压效应、约束、强度退化和剪切软化。在开发的双轴钢筋混凝土模型中，首先建立单轴模型，然后由单轴模型组装双轴模型。首先，报告了所提出的混凝土单轴本构模型。通过根据网格大小调整混凝土模型的下降分支来降低模型的网格敏感性。其次，共报告了五个混凝土双轴本构模型，涵盖了工程设计中的广泛模拟要求。第三，讨论了所提出的具体模型在 ABAQUS 隐式和显式求解器中的数值实现。随后，修改后的双向固定角度裂纹模型通过单调和滞后面板测试进行验证。当单元数从 4 增加到 400 时，有限元模型表现出很小的网格敏感性。开发的模型准确地预测了面板的挤压效应和软化效应。最后，模拟了先前在侧向载荷下对两个核安全壳进行的测试，修改后的双向固定角裂纹模型在预测初始刚度、极限容量和挤压效应方面表现出足够的准确性。