Experimental Study on the Effects of Fire on the Axial Strength of Hollow RC Columns

Understanding the performance of the concrete members during fires is crucial for safety and risk assessment. The present study investigates the performance of reinforced concrete hollow columns when exposed to fire flame. Sixteen hollow columns, each with a uniform height of 1000 mm and a cross-section of 150 mm × 150 mm, were subjected to axial compression load until failure. The main parameters considered were the hollow diameter and flame temperature. The hollow diameter ranged from 25.4 mm to 76.2 mm, while the flame temperature varied from 300 °C to 700 °C in 200 °C intervals over a one-hour duration. The results indicated that the axial load capacity of columns has dropped as the fire flame temperature increased for the same hollow size. The reduction in axial load capacity ranged from 20.10% to 68.42% for temperatures between 300 °C and 700 °C. In addition, under identical burning conditions, the specimen with a bigger hollow diameter exhibited a higher load capacity reduction. Finally, beyond a hollow diameter of 25.4 mm or a fire flame temperature of 300 °C, the axial stiffness of columns was significantly reduced.