Performance deterioration of corroded RC beams and reinforcing bars under repeated loading

• Failure mode of corroded RC beams under repeated loading was investigated.
• Flexural stiffness change of corroded RC beams under repeated loading has two obvious features of stages.
• Characteristics of stress–strain curves for reinforcing bars after corrosion fatigue changed significantly.
• Modified calculation formula for flexural stiffness of corroded RC beam under repeated loading was presented.
• Constitutive relation model for the reinforcing bar after corrosion fatigue was presented.

Based on the accelerated corrosion test and fatigue loading test of RC beam specimens and the static tensile test of reinforcement specimens that were removed from the beam specimens after fatigue loading test, failure mode and flexural stiffness of corroded RC beams under repeated loading and mechanical behavior of reinforcing bars after corrosion fatigue were studied. We find that flexural stiffness change of corroded RC beams under repeated loading has two obvious features of stages, namely, slowly decreasing stage and stable stage. Considering the effects of corrosion and fatigue respectively, stiffness correction coefficients were introduced to quantitatively present the modified calculation formula for flexural stiffness of corroded RC beam under repeated loading. After corrosion fatigue, characteristics of stress–strain curves for reinforcing bars changed obviously: the yield strength decreased, percentage of elongation shortened, features of yield plateau changed. Mild steel changed into hard steel to varying degrees. Combined with the experimentally obtained stress–strain curves, constitutive relation model for the reinforcing bar after corrosion fatigue was quantitatively presented. The results of this study can provide reference for calculation and assessment of corroded RC bridge structures under long-term live load.