Experimental and Mechanical-based Analysis of Fatigue-Induced Pull-Out Degradation in Single Hooked-End Steel Fiber in Fiber-Reinforced Cementitious Composites

Abstract

Fatigue analysis of steel fiber-reinforced cementitious composites (SFRCC) is crucial for structural design and safety assessment under repeated loading cycles. Experimental studies have demonstrated cyclic degradation in SFRCC, attributed to the deterioration of fiber-bridging strength. However, a comprehensive analytical quantification of fatigue-dependent parameters for deformed fibers across multiple scales remains limited. This study aims to characterize the fatigue dependency of SFRCC at the fiber-scale through analytical models based on experimental investigations. Static and fatigue pull-out tests were conducted on single hooked-end steel fibers embedded with a 20 mm length. Fibers were initially pulled to varying displacement levels (0.125, 0.25, 0.50, 0.75, 1.00, 2.50, 4.00, and 5.00 mm) before cyclic loading. Fatigue tests at a frequency of 5 Hz continued up to two million loading cycles or until pull-out failure, during which the fiber hook was progressively straightened. X-ray Computed Tomography (CT) scans were employed to investigate the associated failure mechanisms. A novel mechanical model was proposed to capture the displacement evolution rate during fatigue pull-out loading and predict the fatigue life. This model demonstrates a satisfactory correlation with the experimental results, providing a valuable tool for understanding and predicting the fatigue behavior of SFRCC.