Deflection Calculation of Fatigue-Damaged RC Beams Under Chloride Exposure

A prediction methodology for the mid-span deflection of fatigue-damaged RC beams subjected to chloride-induced corrosion is proposed, incorporating the coupled effects of fatigue stress levels and localized pitting corrosion in steel reinforcement. The reliability of the methodology is validated through experimental comparisons. The effects of fatigue stress are quantified via two mechanisms: degradation of the concrete elastic modulus and the development of fatigue-induced cracks in the steel reinforcement, which reduces its effective cross-sectional area. Pitting corrosion is simplified as equivalent surface cracks. To determine the chloride concentration within the concrete cover for predicting steel pit depth, a 3D meso-scale model is developed to simulate chloride ingress in fatigue-damaged concrete. The concrete is treated as a three-phase composite composed of coarse aggregate, mortar matrix, and the interfacial transition zone (ITZ), and each phase has its own diffusion coefficient. Based on previous chloride concentration tests, the effect of fatigue loading is considered by the accelerated and depth-dependent diffusion coefficients. Based on the meso-scale simulation results, mid-span deflections of fatigue-damaged RC beams under varying chloride exposure durations are predicted. The findings conclusively demonstrate that, under prolonged chloride erosion, the mechanical stress state remains the predominant factor governing structural deformation, overshadowing time-dependent corrosion effects.