Abstract
A high-strength concrete and mortar subjected to compressive fatigue loading were comparatively investigated using experimental and computational techniques. The focus of the investigations was on the influence of the coarse aggregate in high-strength concrete. Accordingly, the fatigue behaviour was analysed experimentally using the macroscopic damage indicators strain, stiffness and acoustic emission hits. The results clearly show differences in the fatigue behaviour between the concrete and the mortar, especially at the lower stress level investigated. The basalt coarse aggregate here improves the fatigue behaviour of the concrete. Indication of a negative effect can be seen at the higher stress level. A finite element approach with a gradient-enhanced equivalent strain-based damage model combined with a fatigue model was used for the computational simulation of the fatigue behaviour. The damage model includes a differentiation between tension and compression. The fatigue model follows the assumption of the reduction in the material strength based on the accumulated gradient-enhanced equivalent strains. A random distribution of spherically shaped basalt aggregates following a given particle size distribution curve is used for the simulation of concrete. The comparison of the experimentally and computationally determined strain developments of the concrete and mortar shows very good agreement.
Highlights
The application of concrete with increasingly higher compressive strengths enables the realisation of more slender concrete structures
After focusing mainly on the number of cycles to failure, the latest research is especially focused on the concrete fatigue behaviour or rather damage development [1,2], which can be described by different damage indicators, such as strain, stiffness and, as an innovative experimental approach, acoustic emission (AE)
At the lower stress level, on the other hand, the presence of the coarse aggregate leads to an improved fatigue behaviour
Summary
The application of concrete with increasingly higher compressive strengths enables the realisation of more slender concrete structures. During the last few decades, the mechanical and numerical modelling of fatigue has generally been based on phenomenological model assumptions, such as the well-known Paris law, which was used explicitly as part of the models This means that a specific increase in damage or a particular crack increment prescribed by Paris law is assumed for every load cycle and the actual damage mechanisms in the background are not scrutinised. The general challenge in developing and validating computational models is the limited knowledge regarding the important material behaviour patterns and their interpretation on a small length scale leading to the observable macroscopic material behaviour This concerns those models that can be applied to simulate the complex processes of fatigue damage accumulation in concrete’s microstructure. A new modelling approach for the simulation of the concrete and mortar’s fatigue behaviour is described and the numerical results received are presented comparatively and discussed with the fatigue behaviour determined experimentally
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