Flexural fatigue behavior of FRP-reinforced UHPC tubular beams

Fiber-reinforced polymer (FRP) reinforced ultra-high-performance concrete (UHPC) tubular structures offer excellent corrosion resistance and mechanical properties, making them ideal for offshore construction applications such as bridge decks and girders. This paper investigates the flexural performance of FRP-reinforced UHPC tubular beams under static and fatigue loading, focusing on the effects of polyethylene (PE) and steel fibers. Results show that steel fiber-reinforced beams have higher load resistance under static loads, while both fiber types exhibit similar fatigue life under equivalent fatigue loads, despite differences in crack evolution and strain. Steel fibers reduce GFRP bar deformation but cause faster UHPC degradation. Fatigue tests revealed up to a 48.86 % reduction in residual load capacity for PE fiber-reinforced beams. A fatigue endurance limit of 0.5 Pu is recommended for FRP-UHPC tubular structures in fatigue-critical applications. • Static and fatigue flexural behavior of FRP reinforced UHPC tubular beams are comprehensively explored. • Steel fibers provide better stiffness at the post-cracking stage compared to PE fibers. • PEU-FA5 endured 2 million loading cycles and retained 93.92 % of its load-resistance capability. • FRP-UHPC tubular beams reinforced with steel fibers show comparable fatigue life to those reinforced with PE fibers. • Fatigue endurance limit of 50 % load capacity is proposed for FRP-UHPC tubular beams.