Fatigue-dependent pull-out degradation of inclined hooked-end steel fibers in SFRCC: Experiments and mechanics-based modeling

This study investigates the fatigue-induced degradation of fiber-bridging capacity in steel fiber-reinforced cementitious composites (SFRCC) under cyclic loading. Experimental and analytical investigations were employed to quantify interfacial degradation mechanisms. Hooked-end steel fibers embedded at 0°, 30°, 45°, and 60° inclinations within a concrete matrix were subjected to static and cyclic pull-out tests. Fibers were initially pulled out to simulate crack formation, followed by fatigue loading up to two million cycles or failure. Two failure mechanisms were observed: fiber pull-out and rupture, further validated through X-ray CT scans. Fiber rupture dominated at higher inclination angles, with significant surface matrix spalling. Fibers at 45° exhibited the highest degradation rate, with accelerated displacement evolution and shortened fatigue life. Mechanics-based models were developed to predict displacement evolution, fatigue life, and rupture behavior, demonstrating strong alignment with experimental results. The findings enhanced understanding of fatigue damage evolution in SFRCC and provide reliable frameworks for performance prediction.