‘‘Behavior of strengthened reinforced concrete columns after exposure to elevated temperature”

Columns are critical to structural integrity, as elevated temperatures can weaken them and cause collapse, necessitating detailed studies on their behavior under such conditions. This study investigates the axial capacity of eleven heat-damaged reinforced concrete (RC) columns through experimental and numerical methods. Columns (200 × 200 × 1200 mm) were subjected to temperatures of 400°C and 600°C for 90, 120, and 150 minutes, followed by natural cooling. Strengthening was applied using RC jacketing, steel jacketing, and CFRP wrapping sheets. Variables included temperature, exposure duration, different strengthening techniques, concrete compressive strength, and concrete cover size. The compressive strength reduction reached a maximum of 44% after 150 minutes of fire exposure. Strengthening techniques and increasing concrete cover improved the overall behavior and ultimate load capacity. Numerical analysis using ABAQUS closely matched experimental results, confirming its accuracy in predicting column behavior under elevated temperature-damaged conditions. The findings can assist the structural engineer in determining the most effective strengthening technique for such columns and enhancing their performance after exposure to elevated temperatures.