Effect of Heating Level on the Contribution of CFRP Bars in the Axial Load-carrying Capacity of RC Columns

This paper investigates experimentally the effect of elevated temperatures on the behavior of concrete columns, internally reinforced with longitudinal carbon fiber reinforced polymer (CFRP) bars. Eight columns were reinforced with steel and CFRP bars each, cast, and cured for 28 days before exposed to elevated temperatures of (200–400 °C). The heated columns were allowed to cool down to room temperature before tested for concentric axial loading response using a universal testing machine of 2000 kN capacity. The results indicate that the axial load-carrying capacity, stiffness, and toughness of the columns significantly reduced with elevated temperatures in excess of 200 °C. The columns, reinforced with CFRP bars, maintain only 43% of its original axial load capacity when heated at 400 °C, whereas, corresponding ones with steel reinforcement maintain 79%. The study revealed that ignoring the contribution of CFRP bars to axial load capacity tends to underestimate the actual load capacity of relevant columns; especially when pre-subjected to temperatures of less than 400 °C prior to testing.