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Abstract

This research investigates the low-cycle fatigue behaviour of reinforcing bars and the seismic performance of reinforced concrete bridge columns, considering ASTM A955 Grade 520 stainless steel and CSA G30.18 400W conventional reinforcement bars. The study first presents an assessment of both types of reinforcement bars under monotonic and cyclic loads, and analyzes their mechanical properties and low-cycle fatigue performance. Cyclic loading tests were conducted on deformed bars at various strain amplitudes and unsupported lengths to evaluate the impact of inelastic buckling. Results revealed that ASTM A955 Grade 520 bars outperformed the CSA G30.18 400W bars in terms of cycles to failure and energy dissipation, particularly at higher strain amplitudes. Building on these findings, four circular RC bridge columns were tested under lateral cyclic loading to assess their seismic behaviour. Two columns were reinforced with ASTM A955 Grade 520 stainless steel, and two with CSA G30.18 400W conventional steel, each with an aspect ratio of 3 and 6. The seismic performance was evaluated based on hysteretic response, ductility, energy dissipation, plastic hinge length, and performance damage states, including concrete cracking, cover spalling, stirrup yielding, bar buckling, and bar fracture. The column reinforced with stainless steel columns exhibited similar hysteretic behaviour to columns reinforced with conventional steel up to ductility demand levels of 4. At failure, the former demonstrated superior drift ratios and did not exhibit bar fracture. The performance damage states showcased material-specific responses and highlighted limitations of code-prescribed strain criteria for ASTM A955 Grade 520 reinforcement. Finally, seismic fragility and resilience assessment of RC bridge columns reinforced with ASTM A955 Grade 520 and CSA G30.18 400W steel were conducted, considering both crustal and subduction earthquakes. In both scenarios, the stainless steel reinforcement reduced the seismic vulnerability of RC columns across various damage limit states. Overall, the research underscores the excellent low-cycle fatigue performance and the potential benefits of stainless steel as seismic reinforcement. It provides essential data aimed at informing the development of performance-based seismic design guidelines for concrete columns reinforced with stainless steel. These advancements contribute to the development of more resilient infrastructure in high seismic zones.