Residual monotonic mechanical properties of bimetallic steel bar with fatigue damage

When a reinforced concrete structure experiences an earthquake and does not collapse, irreversible damage in the reinforcement is caused by the fatigue load, which affects the residual bearing capacity of the structure significantly. Stainless-clad bimetallic steel bars (BSBs) are a new type of coated reinforcement with effective resistance to corrosion. In this study, to accurately evaluate the residual bearing capacity of a concrete structure reinforced with BSBs following an earthquake, it is tested with different fatigue damage ratios. Thereafter, the monotonic stress-strain nonlinear performance, failure behaviour, and residual mechanical properties of BSBs with fatigue damage are explored. The evolution law of the mechanical properties of BSBs with fatigue damage is analysed. A monotonic stress-strain model of the BSB that considers the impact of fatigue damage is proposed. The test results indicate that the stainless-steel cladding of the BSB does not demonstrate apparent buckling following fatigue damage. Cracks are observed on both sides of the rib teeth. When the fatigue damage ratio is 0.6, a fracture occurs at the maximum crack caused by the fatigue damage. When the fatigue damage ratios are 0.2 and 0.4, fractures occur in the necking region of the upper or lower part of the specimen. Fatigue damage leads to the disappearance of the yield platform from the monotonic stress-strain curve of the BSB. The yield strength of the BSB decreases significantly owing to the fatigue damage ratio. The ultimate strength is barely affected by the fatigue damage ratio. Fatigue damage has an adverse effect on the deformation capacity of the BSB. With an increase in the fatigue strain amplitude and fatigue damage ratio, elongation following the fracture of the BSB gradually decreases. This study provides solid theoretical and experimental bases for the engineering application of BSBs, particularly in the post-earthquake evaluation of concrete structures reinforced with BSBs.