Performance Enhancement of Pre-loaded RC Short Columns Damaged by High Temperature Using CFRP Wrapping

This study investigates the effectiveness of rehabilitating fire-damaged reinforced concrete (RC) short columns by removing the deteriorated concrete cover, replacing it with normal concrete (NC), and strengthening the columns using carbon fiber reinforced polymer (CFRP) sheets.

An experimental program was conducted on nine small-scale RC column specimens subjected to eccentric axial loading with an eccentricity of 45 mm. The columns were exposed to fire temperatures of 500 °C and 700 °C for durations of 60 min and 120 min using a specially designed furnace, while sustaining a constant axial load equal to 50% Pu. An unexposed control specimen was tested for comparison. After fire exposure, the damaged concrete cover was removed and replaced with NC, followed by full wrapping using CFRP sheets.

The results showed a significant reduction in ultimate load capacity with increasing fire temperature and exposure duration. Fire-exposed specimens exhibited noticeable strength degradation compared to the control specimen. After rehabilitation using NC replacement and CFRP wrapping, the columns demonstrated substantial recovery and enhancement in load-carrying capacity.

The improvement in structural performance is attributed to the confinement effect provided by CFRP sheets combined with the restored concrete cover. The results also highlight the influence of fire severity on residual strength and confirm the effectiveness of the proposed rehabilitation technique under eccentric loading conditions.

Replacing the damaged concrete cover with NC and strengthening with CFRP sheets proved to be an effective rehabilitation technique for fire-damaged RC columns. The proposed method significantly restored and enhanced load-carrying capacity, supporting its practical application for post-fire strengthening under sustained eccentric loads.