基于非局部微平面模型M7的混凝土非线性有限元分析

Nonlinear finite element analysis of concrete structure based on nonlocal microplane model M7

混凝土作为多相复合材料,其力学行为复杂多样,结构响应具有明显非线性,采用宏观本构模型精确描述存在较大难度。基于微观水平的混凝土本构模型——微平面模型M7,通过二次开发接口,将其嵌入具有较强非线性分析能力的通用有限元程序ABAQUS,对混凝土单轴压缩及拉伸、三轴压缩进行了模拟分析,通过与相关试验结果比较,验证了基于微平面模型子程序的有效性;为规避应变局部化引起的网格敏感性问题,将非局部理论引入微平面模型,研究了混凝土矩形面板与三点弯曲梁的应变软化问题。结果表明:微平面模型M7能够较好地模拟混凝土应力-应变全曲线过程,及多种应力状态下的力学行为;结合非局部理论的非局部微平面模型用于混凝土结构的有限元分析,不存在网格依赖性问题,能够给出合理的结构应变软化局部化响应,数值模拟结果合理可靠。

As a heterogeneous composite material,the complicated and various mechanical behavior of concrete and its nonlinear structural response are very difficult to simulate precisely by macroscopic constitutive model. With the secondary development interface,microplane model M7 for plain concrete based on micro-level has been integrated into the general finite element program ABAQUS,which has a strong ability of nonlinear analysis. Concrete specimens under uniaxial compression and tension and triaxial compression are simulated with the proposed program. And the reasonableness of the secondary development of the subroutine is validated by comparing the numerical predictions of proposed program with the test results. To avoid the spurious mesh sensitivity problem induced by strain localization,the microplane model combined with the recently improved nonlocal approach was introduced to study the strain softening of the concrete rectangular plate and the three point bending beam. The results show that the model M7 can simulate the full stress-strain curves of concrete excellently,and be exceptionally well suited for simulating the multiaxial behavior. For nonlinear finite element analysis of concrete structures with nonlocal microplane theory,the reasonable structure strain softening localization response can be obtained without mesh dependence. The numerical simulation results are reasonable and reliable.