Degradation and service life prediction of reinforced concrete beams under coupled fatigue loading and chloride ingress: A review

Reinforced concrete beams, critical load-bearing components in bridge engineering, are subjected to combined degradation of fatigue loading and chloride ingress during service. While fatigue action promotes the initiation, propagation, and coalescence of microcracks, accelerating chloride diffusion, chloride intrusion triggers steel depassivation and rust-induced cracking, gradually reducing load-bearing capacity. This paper systematically reviews relevant research progress in fatigue–chloride coupling, encompassing: (1) material-level studies on fatigue-induced microstructural evolution, accelerated ion transport, corrosion mechanisms, and the degradation of reinforced-concrete bond behavior; (2) component-level investigations from both accelerated scaled tests and long-term exposure experiments, elucidating macroscopic performance deterioration including stiffness decay, residual bearing capacity loss, ductility reduction, and failure mode transitions; (3) development of service life prediction methods, ranging from empirical models, mechanism-driven models, reliability analyses, to artificial intelligence-based prediction approaches. Finally, future research directions are discussed, focusing on cross-scale parameter transfer and coupling mechanisms, and integrating artificial intelligence with structural health monitoring. • Reviews material-level coupling of fatigue cracks, ion transport, and corrosion. • Summarizes component degradation from scaled and long-term exposure beams. • Compares tests and models on stiffness, ductility, and strength degradation. • Evaluates service life prediction models under fatigue–chloride coupling. • Outlines future research needs for realistic coupling tests and model integration.