钢筋混凝土柱破坏过程扩展有限元数值模拟

Simulation of failure process of reinforced concrete columns with extended finite element method

为描述钢筋混凝土柱的破坏过程,分别建立了由三维实体单元和三维杆单元构成的精细化模型以及结合纤维梁单元的纤维梁与实体单元耦合模型。耦合模型中,钢筋混凝土柱下段混凝土和钢筋分别用三维实体单元与三维杆单元建模,通过耦合连接实现精细单元与粗糙单元之间的变形协调。基于混凝土弹塑性本构关系,运用扩展有限元方法模拟钢筋混凝土柱的荷载-位移曲线以及开裂过程,并进行比较。数值模拟与试验结果的比较表明,模拟得到的裂缝位置以及荷载-位移曲线与试验结果吻合较好。扩展有限元具有无需重划网格、无需预设裂纹的优点,能有效地模拟筋混凝土柱的开裂过程。耦合模型具有计算效率高的优势,且能较好地模拟构件的破坏模式。

In this study, for the purpose of simulating the failure process and pattern of reinforced concrete(RC) columns, a fine model with three-dimensional(3 D) solid elements and two coupling finite element models composed of 3 D elements and fiber beam elements are constructed and elasto-plastic analysis of the models are carried out numerically using extended finite element method(XFEM). The concrete and the rebars of the lower part of the specimen are modeled with 3 D solid elements and 3 D truss elements respectively and the upper part of each RC column under different axial load ratios is modeled with fiber beam elements. The 3 D solid elements and the fiber beam elements are coupled at the interface and deformation compatibility condition is met. Two RC specimens with different axial load ratios are simulated and the corresponding load-deformation ration, the cracking patterns and the stress distribution are compared with the experimental measurements. Results show that the load-deformation relation and the crack pattern are in good agreement with the experimental measurements. The combination of XFEM where remeshing and predefining of cracks are unnecessary and the coupling modeling technology using 3 D solid elements and fiber beam elements provides an efficient way for the failure simulation of RC columns.