Comparative Study on the Impact and Static Loading Performance of GFRP-RC Columns

Circular reinforced concrete (RC) columns are commonly used in bridge structures, such as piers, due to their cost efficiency and structural performance. However, these columns are vulnerable to lateral impact loads under extreme conditions, such as collisions from errant vehicles or vessels. Although several studies have examined the low-velocity impact behavior of RC beams, limited research has addressed the dynamic response of axially loaded RC columns under lateral impact. To bridge this gap, the current study investigates the impact performance of axially loaded circular RC columns through low-velocity impact testing. In recent years, fiber-reinforced polymer (FRP) bars have been introduced as alternatives to conventional steel reinforcement because of their high strength-to-weight ratio and excellent corrosion resistance. Despite these advantages, the impact resistance of glass fiber-reinforced polymer reinforced concrete (GFRP-RC) columns is not yet fully understood, particularly under combined axial and lateral impact loads. This experimental study examined two circular GFRP-RC columns fabricated with identical longitudinal and transverse reinforcement ratios. One specimen was tested under impact loading combined with an axial load equal to a specified percentage of its axial capacity, while the second was tested under static loading under the same axial load conditions. The results indicate that the equivalent static force calculated using the AASHTO empirical formula for RC columns with steel reinforcement significantly overestimates the actual impact force in GFRP-RC columns. Since the formula considers only the impact weight and velocity, it may lead to an overly conservative design approach for impact-resistant GFRP-RC structures.