This paper presents an experimental investigation on the rehabilitation of fire-damaged reinforced concrete (RC) columns subjected to sustained eccentric loading using Ultra-High-Performance Concrete (UHPC) jacketing. The experimental program consisted of nine small-scale RC column specimens, including one unexposed control specimen and eight fire-exposed specimens subjected to temperatures of 500 °C and 700 °C for durations of 60 and 120 minutes. During fire exposure, a sustained eccentric axial load corresponding to 50% of the ultimate capacity was maintained to simulate service conditions. The results indicated that fire exposure significantly reduced the structural capacity of the columns. Compared with the control specimen, ultimate load reductions reached 11.65% and 14.11% at 500 °C, and 20.85% and 36.8% at 700 °C for 60 and 120 minutes, respectively. Following removal of the damaged concrete cover, the original cross-section was restored using a 20 mm UHPC jacket without increasing column dimensions. Strengthening resulted in substantial recovery and enhancement of load capacity, with recovery ratios ranging from 104.86% to 157.28% relative to the corresponding fire-damaged specimens. In addition to strength improvement, UHPC confinement significantly enhanced stiffness, ductility, and crack control performance. A clear transition in failure mode was observed after strengthening, shifting from compression-controlled crushing in fire-damaged columns to localized shear behavior in the corbel region under eccentric loading. The strengthening efficiency was more pronounced in severely fire-damaged specimens, highlighting the interaction between fire severity and confinement effectiveness. The findings demonstrate that UHPC jacketing is a highly effective rehabilitation technique for pre-loaded fire-exposed RC columns, providing both recovery of fire-induced degradation and structural enhancement beyond the original reference state.
