Visualisation and micromechanical modelling of internal damage processes due to cyclically loaded high performance concretes, with emphasis on the hygral and thermal boundary conditions

拟议项目的主要目标是开发实验和虚拟数值方法，使材料退化的高性能混凝土疲劳荷载下的评估。研究工作将由一个跨学科研究网络进行，该网络具有明确的任务结构，并在复杂的退化现象之间进行开放的数据交换。为了获得尽可能多的知识，这些子项目将在多尺度方法的背景下进行，明确侧重于选定的高性能混凝土和最主要的影响。研究结果将是一种方法来评估高性能混凝土的损伤过程，而在拉伸和/或弯曲载荷与同时考虑的湿/热边界条件。作为第一种方法，将定义两种高性能混凝土，允许直接比较个别材料的特定损伤影响，以及它们如何影响微观结构循环行为的变化。此外，在循环拉伸和/或弯曲加载试验期间，将通过安装在加载样本表面的连续摄影测量系统检测材料性能的变化。根据这些结果，将创建SN曲线，其中考虑了施加的相对应力/强度差异以及施加到样本的最低应力/强度水平。此外，将使用不同成像技术（如microXCT扫描仪和其他间接分析方法）的组合对未加载和循环加载样本进行比较研究。在此，将特别关注湿度和热边界条件对循环载荷引起的微观结构变化的影响。为了进一步分析所获得的实验数据，将开发一个开放的结构化在线数据库。这将是一个虚拟实验室的一部分，定义的本体，可用于分析高性能混凝土的循环损伤过程。作为多尺度建模活动的一部分，通过进行实验测试验证的模拟结果将是面向对象的虚拟实验室环境的第一个构建块。

Main objective of the proposed project is to develop experimental and virtual numerical methods that enable the assessment of materials degradation in high performance concrete under fatigue loading. The research work will be conducted by an interdisciplinary research network with a clear task structure and an open data exchange among the complex degradation phenomena. For achieving the greatest possible knowledge gain, the sub-projects will take place within the context of a multi-scale approach, with a clear focus on the selected high performance concretes and most dominant impacts. Result of the research will be a method to assess the damage processes of high performance concrete while under tensile and/or flexural loading with a simultaneous consideration of the hygral/thermal boundary conditions. As first approach, two high-performance concretes will be defined that allow for a direct comparison of the individual material-specific damage influences and how they affect the changes in the microstructure cyclic behavior. In addition, during the cyclic tensile and/or flexural loaded tests, the alterations in material behavior will be detected by a continuous photogrammetry system which is mounted at the surface of the loaded specimens. Based on these results, SN curves will be created that are taking into account the applied relative stress/strength difference as well as the lowest stress/strength level applied to the specimens. Furthermore, a comparative study of both the unloaded and cycled loaded specimens will be carried out using a combination of different imaging techniques, such as microXCT-scanner and other indirect analysis methods. In this, particular attention will be given to the influence hygral and thermal boundary conditions have on the microstructural changes due to cyclic loading. For further analysis of the obtained experimental data an open structured online database will be developed. This will be part of a virtual laboratory with defined ontology that can be used for analysis of cyclic induced damage processes in high performance concretes. As part of the multi-scale modeling activities, simulated results validated by the conducted experimental tests will be the first building blocks of the object-oriented virtual lab environment.