摘要
对于断裂的数值模拟一直是一个难点问题,无论在一般固体领域,还是在混凝土结构中。尤其是对于动态断裂问题,其数值模拟更是困难。新近得到广泛运用的内聚单元模型是专门为断裂数值计算而提出来的。内聚模型理论中,断裂认为是一个渐变过程——初始裂纹两侧的分离受到内聚力的阻挠,内聚力与张开量是由内聚关系确定的。内聚模型作为一个完全的断裂理论,不被任何材料特性、有限运动、非比例载荷、动力学或是试件的几何尺寸所限制。已证实此理论对复杂的断裂过程的模拟是有效的,包括:脆性材料的断裂、韧性材料的动态断裂和破碎、混凝土的动态Bazilian测试等等。
本文主要对内聚模型在混凝土断裂数值模拟中的应用做了一些讨论,并推导出了一种简单的二维六结点等参内聚单元,并用Fortran语言编写了含有内聚单元的有限元程序对混凝土切口梁的断裂过程进行了计算。计算结果表明,此方法对于混凝土材料是适用的。
Numerical simulation of concrete fracture is a challenging topic. Concrete crack has in important effect on concrete structure, so it is critical to the calculation of concrete crack properly, especially in dynamic problem. Cohesive element model is regarded as an effective tool to solve the fracture calculation. In the cohesive theory, fracture is regarded as a gradual process in which the separation of the incipient crack flanks is resisted by cohesive tractions. The relation between the cohesive tractions and the opening displacements is governed by a cohesive law. Cohesive models furnish a complete theory of fracture that is not limited by any consideration of material behavior, finite kinematics, non-proportional loading, dynamics, or the geometry of the specimen. The cohesive theory has proved effective in the simulation of complex fracture processes including: the fragmentation of brittle materials; dynamic fracture and fragmentation of ductile materials; and the dynamic Brazilian test for concrete.
In this paper the introduction of the use cohesive element in concrete structure is given, and a kind of 2-D isoperimetric cohesive element is deduced. The fracture process of concrete notch beam is calculated by Fortran programming. The result shows that the method is feasible.
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