Experimental Study on Fatigue Behavior of Deep-Reinforced Concrete Beams with Corroded Reinforcement

RC deep beams are critical load-bearing elements in bridge structures, designed to sustain heavy loads over short spans while being exposed to cyclic loading and aggressive corrosive environments during their service life. This study presents an experimental investigation into the fatigue performance of RC deep beams under varying degrees of reinforcement corrosion. The specimens were subjected to sinusoidal cyclic loading, ranging from 10% to 60% of the beam’s ultimate capacity, at a frequency of 3 Hz. Tensile reinforcements were artificially corroded using the accelerated current method with a 5% NaCl solution as the electrolyte. The fatigue behavior of the corroded beams was evaluated, focusing on the mode of failure, progression of deflection and strain with cycles, stiffness degradation, and fatigue life. The result showed that the fatigue life of corroded specimens decreased by approximately 12%–87% as the reinforcement mass loss increased from 1.7% to 10.1%. While all specimens exhibited the characteristic failure mode of tensile reinforcement fracture, corrosion-induced effects, including bond strength deterioration, stiffness reduction, and longitudinal cracking, significantly impacted the failure mode of beams. To simulate more realistic conditions, the research further explores how the structural behavior is altered when corrosion and fatigue simultaneously progress. A comparative analysis quantifies the additional damage sustained by specimens exposed to simultaneous corrosion-fatigue loading relative to precorroded beams before fatigue testing. The relationship between the degree of corrosion and fatigue life degradation demonstrated that approximately 1% rebar mass loss resulted in a 6.9% reduction in fatigue life for precorroded specimens, compared with a significantly higher reduction of 40.5% for specimens undergoing simultaneous corrosion. This emphasizes the critical need to investigate the coupled effects of corrosion and cyclic loading on degradation mechanisms over service life. Furthermore, the results demonstrate that overlooking the synergistic interaction between fatigue and corrosion results in a significant overestimation of fatigue life, leading to substantial inaccuracies in the performance predictions for RC bridges subjected to corrosive environments.