Concrete compressive strain behavior and magnitudes under uniaxial fatigue loading

Recent advances in concrete technology and construction have promoted an increasing utilization of concrete in fatigue-critical structures, such as wind turbine towers. While research into concrete fatigue is not a new topic and has been going on for several decades, a large majority of this research has primarily been focused on the determination of concrete fatigue capacity. However, understanding and advancing concrete fatigue behavior (e.g., fatigue stress vs. strain response) has received limited attention, even though this is also crucial, especially considering the inherently nonlinear behavior of concrete. To address this knowledge gap and further advance our understanding of concrete fatigue behavior, an experimental investigation consisting of uniaxial compressive fatigue testing of concrete cylinder specimens until failure was undertaken, and axial strains were recorded throughout the duration of fatigue loading. The behavior and evolution of concrete axial strains, including the rate of accumulation of strains, through the fatigue loading process were extensively analyzed and are reported. Additionally, the influence of key parameters, such as peak stress levels and number of cycles to failure, on peak strain evolution were investigated and are described. Magnitudes of peak axial strain at the end of the stable strain accumulation phase, as well as at failure, are also reported, and recommendations are made for estimating strain magnitudes at these critical junctures when conducting fatigue analysis and design. The results will help advance the understanding of concrete axial strain behavior under compressive fatigue loading. The results also provide guidelines for estimating the magnitudes of concrete strains under fatigue loads, which in turn will be beneficial to designers, as it allows them to also consider structural performance during the analysis and design of fatigue critical concrete structures.