Experimental Behavior of GFRP Bar-Reinforced CFRP Strip Tie-Confined Normal-Strength Concrete Columns under Different Loading Conditions

In this study, a total of 10 steel and glass fiber-reinforced polymer (GFRP) bar-reinforced normal strength concrete (NSC) specimens with a square cross section of 200 mm x 200 mm were experimentally tested up to failure under different loading conditions. Out of the 10 specimens, 8 specimens had a height of 800 mm and were tested as columns under concentric and eccentric axial loads. The remaining two specimens had a length of 1,500 mm and were tested as beams under four-point bending. The tested specimens were utilized to investigate the efficiency of carbon fiber-reinforced polymer (CFRP) strip ties (CSTs) in transversely confining NSC specimens. Two configurations of CSTs were used: a square (S) configuration and a square overlapping square (SS) configuration. The experimental results indicated that the peak axial load and ductility of the concentrically loaded GFRP bar-reinforced concrete specimens were lower than those of steel bar-reinforced specimens. The peak axial load and ductility of the concentrically loaded GFRP bar-reinforced concrete specimens with SS configuration were about 49% and 100%, respectively, higher than those of GFRP bar-reinforced concrete specimens with S configuration. Also, the GFRP bar-reinforced concrete specimens tested under eccentric loading and four-point bending achieved higher peak axial loads, flexural loads, and bending moments at the second peak loads than the corresponding steel bar-reinforced specimens.

Automated summary

This study experimentally tested the failure behavior of 10 steel and glass fiber-reinforced polymer (GFRP) bar-reinforced normal strength concrete (NSC) specimens under different loading conditions. The results indicated that the GFRP bar-reinforced specimens exhibited lower peak axial load and ductility under concentric loading compared to steel bar-reinforced specimens, but higher peak axial load, flexural load, and bending moment at the second peak load under eccentric loading and four-point bending.