Fatigue of structural concrete driven by a cumulative measure of shear strain

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The major objective of the project is to develop a consistent theoretical, numerical and experimental framework for analysis and characterization of fatigue behavior of concrete. The framework will provide the basis for a deeper understanding of damage mechanisms driving the fatigue propagation of in concrete at subcritical levels of loading. The improved reflection of the fatigue phenomenology compared to the state-of-the-art methods will reduce the number of expensive experiments needed for reliable characterization of high cycle fatigue response. The goal of the theoretical and numerical development is to establish a multi-scale modeling framework based on thermodynamically consistent representation of the dissipative mechanisms associated with cumulative cyclic deformation at subcritical levels of loading. By capturing the key dissipative mechanisms, we will be able to significantly enhance the validity and efficiency of fatigue models for concrete structures. The strategy will consistently combine discrete models of the material structure at the mesoscale and macroscopic phenomenological models of the microplane type. At the same time, it will introduce the possibility to devise an accelerated time integration scheme for an efficient simulation of high-cycle fatigue response. The proposed multi-scale modeling strategy will stimulate the development of a systematic calibration and validation methodology consisting of a sequence of elementary test setups. Systematic test methods will be deployed with the goal to isolate particular effects of fatigue behavior of concrete in order to uncover and describe their relation to the postulated elementary dissipative mechanisms. The ambition of this development is to provide a sound explanation of still puzzling fatigue phenomena, like the fundamentally different fatigue behavior of concrete under tensile and compressive cyclic loading with variable amplitudes.In comparison to the state-of-the-art methods of fatigue characterization, the proposed approach will establish the basis for more efficient characterization and assessment of fatigue behavior of reinforced concrete. In the long run, the developed methods will contribute to formulation of reliable and economic design concepts and codes for structural concrete exposed to fatigue loading. The proposed research project will combine expertise of the two partner teams in different disciplines. In particular, discrete, mesoscale modeling and efficient time-integration along the lifetime domain will be the focus of the team at Brno University. The macroscopic, phenomenological modeling and experimental methods will be developed at RWTH Aachen University.