Experimental and theoretical study of GFRP hoops and spirals in hybrid fiber reinforced concrete short columns

Literature is deficient in exploring the structural behavior of concrete columns reinforced with glass fiber reinforced polymer (GFRP) bars and hybrid fibers. In the present study, the hybrid fiber reinforced concrete (HFRC) consisted of steel fibers and polypropylene fibers. A total of twelve GFRP reinforced HFRC (GHC) columns (250 mm in diameter and 1150 mm in height) were fabricated using longitudinal GFRP bars and transverse GFRP hoops/spirals and tested to failure under different loading conditions. The testing results concluded that all the GHC columns presented similar failure modes with the rupture of GFRP bars and GFRP hoops/spirals. The decrease in the spacing of GFRP transverse reinforcement resulted in an improvement in the axial strength (AS) and ductility of GHC columns. The eccentricity of loading resulted in a significant reduction in the AS of GHC columns. The proposed empirical model based on an experimental database of 270 fiber reinforced polymer reinforced concrete columns presented a good behavior for the experimental results. The comparative investigation solidly verifies the accuracy of the newly proposed empirical model for predicting the AS of GHC columns by assuming the compressive involvement of GFRP bars and the lateral confining pressure due to transverse GFRP reinforcement.