Extension and verification of an energetic fatigue model for concrete under dynamic compressive loading

风力涡轮机以及铁路或公路桥的结构都是高动态应力的。在混凝土和其他材料中，动应力会导致变形和破坏过程，最终可能导致结构倒塌。这些变形和损伤过程统称为材料疲劳。虽然上述结构的主体都是混凝土结构，但并没有统一的模型来描述混凝土在循环荷载作用下发生的变形和损伤过程。已发表的材料模型没有得到充分的验证，也没有考虑混凝土徐变的影响，徐变不可避免地与循环应力平行发生。它被认为是描述混凝土疲劳的最有前途的模型之一。这一扩展特别包括获得混凝土徐变。因此，将在小型混凝土试件上进行大量的试验，以将循环荷载引起的变形和损伤过程与徐变变形过程分开。此外，蠕变相关的应力水平将被确定为循环应力值的函数。扩展疲劳模型将在实验结果的基础上，在系统协调的实验过程中进行最后的验证。在未来，这应该有机会通过考虑疲劳和徐变过程来描述混凝土梁或结构的疲劳过程。由此得到的模型能够考虑循环加载的混凝土结构和部件中的应力重新分布，并利用未使用的系统资源。

Structures for wind turbines as well as railway or highway bridges are high-dynamically stressed. The dynamic stresses are leading in concrete, as well as in other materials, to deformation and damage processes, which can end in the collapse of the structure. These deformation and damage processes are called in general as material fatigue.Although the main part of the above mentioned structures are built out of concrete no consistent model to describe the occurring deformation and damage processes in concrete under cyclic loading exists. In literature published material models are neither sufficiently validated nor consider the influence of concrete creep, which occurs inevitably in parallel with the cyclic stresses.The submitted research project aims to expand an existing fatigue model for concrete, which is taken from literature. It is considered to be one of the most promising models for describing concrete fatigue. The extension consists in particular the acquisition of concrete creep. Therefore extensive experiments will be performed on small-scale concrete specimens to separate the deformation and damage processes resulting of cyclic loading from creep deformation processes. In addition, a creep-relevant stress levels will be determined as a function of the cyclic stress values.The extended fatigue model will conclusively verified in the course of systematically coordinated experimental programs on the basis of the experimental results. In future this should give the opportunity to depict the fatigue processes of concrete beams or structures by keeping fatigue and creep processes into consideration. The resulting model enables to consider stress redistributions in cyclically loaded concrete structures and components and to utilize unused system resources.