Numerical simulations of multiaxial damage behaviour of concrete using the method of discrete elements

该项目的目的是探索离散元方法在混凝土准静态和动态材料行为方面的潜力，并深入了解裂缝的演变和破坏机制。其目的尤其包括使用相同的基本模型方法和基本相同的模拟代码来研究材料在不同加载条件下的行为。DEM模拟允许在不同加载条件和加载速度下使用相同的虚拟试件。用于计算相互作用粒子的接触力的基本接触法和接触法的参数只是先验假设。没有关于潜在裂缝的假设或元素，也没有破坏模型。基于碎裂和细观结构重排的效应是模拟的结果。此外，离散元模拟适合于分析冲击情况下材料在高加载速度下的行为。由于基于粒子的特性和牛顿第二定律的使用，DEM模拟可以定性和定量地研究与冲击波在混凝土中传播有关的复杂动力学现象。作为该项目的一部分，将进一步开发离散元模拟，并考虑到实验室实验的构思和设计的数值工具。实验结果的解释和外推是离散单元数值模拟的进一步应用。在拟议的项目阶段，计划使用虚拟均匀试件和细观结构试件进行准静态载荷和冲击载荷下的研究，以及应变率效应的研究。

The aim of the project is to explore the potential of the discrete element method with regard to the quasi-static and dynamic material behaviour of concrete and to obtain insights into crack evolution and damage mechanisms. The aim includes, in particular, the investigation of material behaviour under different loading conditions using one and the same basic model approach and the principally same simulation code. DEM simulations allow to use the same virtual specimens under different loading conditions and loading velocities. The underlying contact approach which is used for the calculation of the contact forces of interacting particles and the parameters of the contact approach are the only a priori assumptions. No assumptions or elements regarding potential cracks and no damage model are included. Effects based on fragmentation and mesostructural rearrangement are the result of the simulation instead.Furthermore, discrete element simulations are suited for the analysis of the material behaviour under high loading velocities as they occur in impact situations. Due to the particle-based character and due the usage of Newtons second law the DEM simulations allow the qualitative and quantitative study of the complex dynamic phenomena related to the shock wave propagation in concrete. As part of the project, discrete element simulations are to be developed further with a numerical tool for conception and design of laboratory experiments in view. The interpretation and extrapolation of experimental results are further applications of numerical simulations using discrete elements. Investigations under quasi-static load and under impact load using virtual homogeneous specimens and specimens with mesostructure as well as investigations of the strain rate effect are planned within the proposed project phase.