Compressive Performance of Partially CFRP-Confined Square Seawater–Sea Sand Concrete Columns with Internal Epoxy-Coated Reinforcement

Abstract

This study first presents an experimental investigation on the compressive behavior of carbon fiber–reinforced polymer (CFRP)-confined square seawater–sea sand concrete (SSC) columns with embedded epoxy-coated reinforcement (ECR). Thirty-three columns were tested to explore the influence of several parameters, including clear spacing ratios, FRP wrapping schemes, FRP volumetric ratios, and internal steel reinforcement ratios. Test results reveal that the location of CFRP strips with respect to the steel hoops has a significant impact on the mechanical behavior of specimens, especially for the deformation capacity. Furthermore, more obvious improvements of strength and ductility are detected for the reinforced columns with smaller clear spacing ratios and higher volumetric ratios of FRP wraps. In specific, the maximum enhancements of load capacity and ductility index for the reinforced SSC specimens with two-layer CFRP strips are 11.8% and 92.9%, respectively, while the improvements increase to 15.6% and 189.2% when the thickness of CFRP jackets doubles. A regression-based stress–strain model is developed to evaluate the ultimate conditions of FRP partially wrapped concrete columns, and a better agreement can be achieved by the developed model compared with other existing models. Finally, a simple expression is also proposed based on the experimental observations, which can accurately predict the load capacity of plain and reinforced concrete columns wrapped with FRP strips.