Axial compression performance of <scp>CFRP</scp> ‐strengthened reinforced concrete columns under sustained load and corrosion damage

Abstract This study investigates the axial compression behavior of reinforced concrete (RC) columns strengthened with carbon fiber‐reinforced polymer (CFRP) jackets after experiencing combined damage from sustained loading and reinforcement corrosion. Fourteen rectangular RC column specimens were fabricated with different sustained load levels and corrosion degrees. A self‐designed device was developed to simultaneously apply sustained loading and accelerated corrosion, producing target corrosion levels of 0%, 10%, and 20%. After the coupled damage process, selected specimens were strengthened using a single‐layer CFRP jacket and tested under axial compression. The effects of sustained loading and corrosion on failure mode, load–displacement response, stiffness, ductility, and bearing capacity were analyzed. The results indicate that sustained loading generally reduces the actual corrosion degree of reinforcement. CFRP strengthening significantly improves the axial performance of damaged columns, increasing the load‐bearing capacity by 24.3%–85.0%, the ductility coefficient by 7.9%–97.0%, and the stiffness by 7.6%–44.7%. Strengthened columns exhibited a drum‐shaped failure with CFRP rupture occurring at approximately one‐third of the column height, suggesting that additional confinement may be required in this region in practical applications. The results also show that corrosion damage enhances the confinement effectiveness of CFRP, whereas sustained loading weakens it. Finally, a calculation method for predicting the bearing capacity of CFRP‐strengthened RC columns subjected to combined sustained load and corrosion damage is proposed and validated against experimental results. The proposed model provides a reliable approach for evaluating the residual capacity of deteriorated RC columns strengthened with CFRP.