Impact of deformation history on the resistance of concrete and fibre-reinforced concrete to fatigue damage
An experimental and analytical study into the impact of deformation history on the deformation response of conventional and fibre-reinforced concrete was conducted. Experiments included monotonic quasi-static and dynamic tests of two series of samples. Ultrasonic and gravimetric homogeneity control by mass was performed prior to mechanical tests. Prismatic reference samples were tested under uniform deformation velocity (0.004 mm/s) on an Instron 5989 complex with automatic recording of deformations, loadings, time and absorption energy. Deformations were measured in both directions at the total base using system ( Instron ) extensometers. The paper analyses the experimental results on the fatigue behaviour of conventional and polypropylene fibre-reinforced concrete subjected to two-stage cyclic stress with various amplitudes. Parameters of linear and bulk deformability were used as a characteristic under control for low-cyclic fatigue. The fatigue resistance of concrete and fibre-reinforced concrete was assessed by comparing the corresponding characteristics of sample deformation under various modes of cyclic action. Relative similarities in the parameter dynamics of controlled low-cyclic fatigue show significant differences in quantitative values. It was established that the frequency and sequence of moderate ( з ≤ R<sup>н</sup><sub>crc</sub> ) actions have a limited effect on fatigue resistance. The composite behaviour at high-level cyclic stress depends on the deformation history.