Axial performance of hollow concrete columns reinforced with GFRP composite bars with different reinforcement ratios.

Abstract A hollow concrete column (HCC) is a structurally efficient construction system and uses less material. Conventionally, HCCs are reinforced with steel bars, which are prone to corrosion. This study explored the use of glass-fiber-reinforced-polymer (GFRP) composite bars as reinforcement for HCCs and evaluated the effect of the reinforcement ratio on HCC structural behavior. A total of six HCCs reinforced longitudinally with GFRP bars with different reinforcement ratios (1.78%, 1.86%, 2.67%, 2.79%, 3.72, and 4.00%) were prepared and their behavior was investigated. The different reinforcement ratios were achieved by changing the bar diameter (12.7 mm, 15.9 mm, and 19.1 mm) and number of bars (4, 6, 8, and 9 bars). The results show that increasing the diameter and number of bars enhanced the strength, ductility and confinement efficiency of HCC. For columns with equal reinforcement ratios, using more and smaller-diameter GFRP bars yielded 12% higher confinement efficiency than in the columns with fewer and larger-diameter bars. The crushing strain of the GFRP bars embedded the HCC was 52.1% of the ultimate tensile strain. Lastly, the axial-load capacity of the GFRP-reinforced HCC can be reliably predicted by considering the contribution of the concrete and up to 3000 μ ε in the longitudinal reinforcement. [ABSTRACT FROM AUTHOR]