Energy dissipation-based approach to stochastic fatigue of concrete considering interacting time and temperature effects

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The need to drastically reduce material consumption and increase the service life of engineering structures urgently requires higher material utilization, accompanied with intelligent maintenance, repair and recycling concepts. The overall objective of the research proposal is to support the necessary innovative development in structural concrete design by deepening the knowledge of the material and structural behavior in the whole range of interacting loading and environmental attack scenarios during the structure’s lifetime. While high-cycle fatigue of metals has been thoroughly studied and scientific results have progressed to engineering practice by providing reliable predictions of fatigue lifetime, the fatigue damage propagation mechanisms in concrete are yet to be fully understood. In spite of a remarkable progress in recent years made in modeling and characterizing the concrete fatigue behavior, many open questions remain that need to be fundamentally addressed in order to develop a deep and general insight into the phenomenology of concrete fatigue. The scientific goal of the research is to develop advanced, thermodynamically consistent numerical modeling approaches and characterization methods that can capture the interplay of dissipative mechanisms governing fatigue behavior on a broader basis than currently possible. To achieve this goal, the existing common meso-macro modeling platform, which reflects fatigue behavior in terms of local cumulative strain evolution, will be extended to include the influence of temperature, loading rate, and time-dependent material changes. The theoretical and numerical developments will be validated by a systematic experimental program providing multiple observation perspectives to the studied phenomena. To maximize the relevance of the research for engineering practice, the randomness inherent to fatigue loading and local material properties will be captured using advanced methods of probabilistic modeling that will be used for statistical characterization of fatigue behavior in terms of S-N curves, fatigue crack propagation criteria, effect of loading sequence and fatigue creep development. This characterization will serve as a basis for refined design and assessment rules in engineering codes.