Eccentric compression behavior of seawater and sea sand concrete columns reinforced with GFRP and stainless steel bars

Abstract

Using FRP bars instead of steel bars to reinforce concrete columns in harsh environments has become an important method for solving corrosion problems. FRP bars have high tensile strength but low compressive strength and high brittleness, while stainless steel (SS) bars have high tensile and compressive strength and good ductility. Therefore, this paper studied the eccentric compression behavior of seawater and sea sand concrete (SSC) columns reinforced with GFRP and SS bars, in which GFRP bars were arranged on the tension side and SS bars were arranged on the compression side to improve the ductility and to analyze the effect of axial stiffness of reinforcement on the N-M interaction diagrams. A total of 48 SSC columns were designed, of which 20 were reinforced with GFRP and SS bars, 14 were reinforced with GFRP bars and 14 were reinforced with SS bars. To analyze the eccentric compression performance of SSC columns and propose the bearing capacity calculation equation, test variables were designed, including the reinforcement type, reinforcement ratio, and eccentricity, to ensure that the equation had certain universal applicability. The three failure modes of compression failure, combined compression-bending failure, and bending failure were found with the increase in the eccentricity for the GFRP and SS bars reinforced SSC (GFRP-SS-SSC) columns. The ductility indices of the GFRP-SS-SSC columns were approximately 1.5 times those of the GFRP bars reinforced SSC columns, which indicated that the ductility could be improved by replacing the compression GFRP bars with SS bars. Finally, the theoretical N-M interaction diagrams were established through the cross-section force analysis and compared with the experimental N-M interaction diagrams. Moreover, the failure mode is influenced by varying the axial stiffness of the longitudinal bars on both sides of the column section by analyzing the N-M interaction diagrams.