Axial compression of seawater sea sand concrete columns reinforced with hybrid FRP–stainless steel bars

Abstract

Using fiber-reinforced polymer (FRP) bars instead of steel bars to reinforce concrete columns in harsh environments has become an important method for solving corrosion problems. The brittleness of FRP bars significantly reduces the ductility of columns. It has been proposed that columns can be reinforced with hybrid FRP and steel bars to improve ductility, but related research is very limited. In this research, the axial compression behaviour of seawater sea sand concrete (SSC) columns reinforced with hybrid FRP bars and stainless steel (SS) bars was studied. In total, 84 SSC columns were designed, including 15 SS reinforced SSC (SS-SSC) columns, 15 glass-FRP (GFRP) reinforced SSC (GFRP-SSC) columns, 45 hybrid FRP-SS reinforced SSC (FRP-SS-SSC) columns and nine plain SSC columns. The failure modes, load-axial displacement curves, bearing capacity, and ductility were analyzed with consideration of the effects of the reinforcement types, reinforcement ratios, and concrete strength. The results showed that ductility could be significantly improved by hybrid reinforcements, and the ductility indexes of the FRP-SS-SSC columns were close to those of the SS-SSC columns. The proposed equation could accurately predict the bearing capacity of SSC columns Furthermore, the theoretical stress-strain relationship for the studied axial compression SSC columns was proposed.

Axial Compression Behavior of Circular Seawater and Sea Sand Concrete Columns Reinforced with Hybrid GFRP–Stainless Steel Bars

“…Moreover, under the same strains of longitudinal bars, the stresses of SS bars are higher than those of GFRP bars, indicating SS bars contributed more than GFRP bars to the peak load. In addition, the strains of concrete and bars at peak are around 2000 µε, which is similar to current studies [13,14,25]. marked on the load-strain curves for SS bars in Figure 12, with the yield strain for the SS bar being 1128 µε.…”

“…The current studies [3,4,10,25] indicate that neglecting the contribution of FRP bars in the calculation of the bearing capacity for axially compressed FRP-RC columns results in conservative results, while considering the contribution of FRP bars provides accurate predictions [3,4,10,25]. Therefore, in this study, the theoretical calculation of the Pmax takes into account the contribution of GFRP bars.…”

“…Therefore, for SWSSC members, hybrid FRP and SS bars can be used to improve ductility. Xu et al [25] investigated the axial compression performance of SWSSC square columns reinforced with hybrid FRP and SS bars. It was found that ductility can be enhanced by hybrid reinforcements.…”

“…Different from Xu et al [25], this paper investigates the axial compression performance of hybrid FRP and SS bar-reinforced SWSSC columns with a circular cross-section. In addition, to fully utilize the yield stage of SS bars, a lower yield strength of SS bars is adopted compared with that of Xu et al [25]. The axial compressive performance of GFRP-reinforced and SS-reinforced columns is comparatively analyzed.…”

“…The load-axial displacement curve, failure mode, bearing capacity, and ductility of SWSSC columns are discussed. In addition, an equation for calculating the bearing capacity is proposed and compared with the results of Xu et al [25]. of results from steel bars and FRP stirrups in reinforced concrete columns.…”