Numerical and experimental investigations on stress redistributions of fatigue loaded concrete structures in the very high-cycle fatigue range

混凝土在疲劳荷载作用下具有复杂的变形特性。这种行为影响混凝土结构截面水平上的应力分布，并对其使用寿命产生积极影响。规范的疲劳分析概念基于S-N曲线。混凝土的变形和由此产生的应力重分布在横截面水平几乎被忽略，从而疲劳应力混凝土结构是不经济地确定根据当前的设计概念，本研究项目的目的是调查的变形行为，特别是应力重分布的疲劳加载混凝土结构。在此框架内，FE模拟以及实验测试进行。模拟的基础上疲劳加载的混凝土应变模型开发的莱布尼茨大学汉诺威的混凝土建设研究所。试验研究是在该所的共振疲劳试验台上进行的。这一全球独一无二的试验台允许在非常高的循环疲劳范围内（即超过1 · 10^7个载荷循环）检查混凝土梁。这是必要的实验研究，因为应力重分布导致非常高的，可持续的荷载循环在混凝土梁。在此基础上，对疲劳荷载作用下混凝土结构的变形特性、应力重分布以及新的设计方案的制定等问题作了概括性的论述。该研究项目的结果可用于风力涡轮机或高速铁路桥梁等高疲劳负载结构的设计。它们使人们有可能走向一个更现实的尺寸，从而更经济和成本效益的疲劳加载混凝土结构的设计。

Concrete has a complex deformation behavior under fatigue loads. This behavior influences the stress distribution on the cross-sectional level of concrete structures and has a positive effect on their service life. The normative fatigue analysis concept is based on S-N-curves. The deformations of the concrete and the resulting stress redistribution at the cross-sectional level are almost neglected, whereby fatigue-stressed concrete structures are not economically determined according to the current design concept.The aim of this research project is to investigate the deformation behavior and in particular the stress redistribution of fatigue loaded concrete structures. Within this framework, FE-simulations as well as experimental tests are conducted. The simulations are based on a strain model for fatigue-loaded concrete developed at the Institute for Concrete Construction of Leibniz University Hannover. The experimental investigations are carried out on the resonance fatigue testing stand of the institute. This worldwide unique testing stand allows the examination of concrete beams in the very high cycle fatigue range, i.e. more than 1 • 10^7 load cycles. This is essential for the experimental investigations, since the stress redistributions cause very high, sustainable load cycles in the concrete beams.The numerical simulations are verified by the experimental investigations. On this basis, general statements can be made regarding the deformation behavior and the stress redistribution of fatigue-loaded concrete structures as well as the formulation of new design proposals. The results of this research project serve the design of highly fatigue loaded structures such as wind turbines or high-speed railway bridges. They make it possible to move towards a more realistic dimensioning and thus a more economical and cost-effective design of fatigue loaded concrete structures.