Hysteretic behavior of pitting-corroded concrete-filled steel tube columns with different strengthened approaches

This study presents an experimental and numerical investigation of the hysteretic behavior of pitting-corroded concrete-filled steel tube (CFST) columns and the efficacy of two reinforcement methods: Carbon Fiber Reinforced Polymer (CFRP) wrapping and Ultra-High-Performance Concrete (UHPC) encasement. Eleven column specimens were tested under constant axial compression and cyclic lateral loading. The influence of pitting corrosion depth and reinforcement type on the failure modes, load-carrying capacity, stiffness, and energy dissipation was examined. Validated numerical analyses were conducted to investigate load transfer mechanisms and perform parametric studies on key geometric and material properties. Based on the findings, modified design equations were developed to predict the load-carrying capacity of corroded and reinforced CFST columns. The results demonstrate that CFRP wrapping exhibits superior performance in enhancing specimen ductility, while UHPC encasement demonstrates significant effectiveness in restoring load-carrying capacity, with capacity and stiffness values exceeding those of the original un-corroded specimen. The findings provide a reliable basis for the seismic assessment and design of repaired CFST columns in corrosive environments.