Nonlinear stress–strain behaviour of corrosion-damaged reinforcing bars including inelastic buckling

In the seismic design and assessment of reinforced concrete structures in earthquake zones buckling of longitudinal reinforcement in plastic hinge regions is an important limit state that needs to be considered. If the structure is located in an environmentally aggressive area, it is also subject to material deterioration over its service life. Corrosion of reinforcement is the most common type of deterioration of reinforced concrete (RC) structures and bridges. In this paper the nonlinear stress–strain behaviour of corroded reinforcing bars has been investigated by extensive experimental testing. The effect of different corrosion levels on the tension and compression behaviour of bars with different slenderness ratios is presented. The results of this study show that a corrosion level above 15% mass loss significantly affects the ductility and plastic deformation of reinforcement in tension and that corrosion changes the buckling collapse mechanism of the bars in compression. The results of buckling tests show that 10% mass loss produces about a 20% reduction in the buckling capacity of corroded bars. The results also show that the distribution of corrosion pits along the length of corroded bars is the most important parameter affecting the stress–strain response in both tension and compression. Furthermore, a constitutive material model to predict the post-yield buckling behaviour of high-strength steel without a yield plateau is also developed. The proposed analytical model is based on Dhakal–Maekawa buckling model. The analytical model has been validated against experimental tests on uncorroded and corroded bars. The results of this corrosion extended buckling model show a good agreement with the physical testing.