Response of columns with steel-FRP composite bars and carbon fibre reinforced polymer mesh fabric stirrups under eccentric loading

The steel-FRP composite bar (SFCB) has superior ductility and corrosion resistance, and is usually employed as longitudinal reinforcement in offshore infrastructures in harsh environments. Nevertheless, the behavior of SFCB reinforced concrete members under eccentric loading, especially in combination with FRP stirrups, remains unclear to date. To address this issue, an innovative approach is adopted in this study, wherein SFCB is employed as the longitudinal reinforcement and carbon fibre-reinforced polymer-mesh fabric (CFRP-MF) as the stirrup, fabricating an innovative corrosion-resistant reinforced concrete column. The eccentric compression performance of 12 concrete columns with different reinforcement types was profoundly investigated. Research outcomes indicated that the failure modes (namely tension and compression damage) observed in columns reinforced with longitudinal SFCBs and CFRP-MF stirrups were comparable to those of conventional steel reinforced concrete (RC) counterparts. However, notable advancements were observed in terms of effectively controlling crack development within the column. The incorporation of CFRP-MF stirrups in the column exhibited a significant confining effect, leading to enhanced compression performance under small eccentricities compared to conventional RC columns. However, in cases involving large eccentricities, the replacement of longitudinal reinforcements with equal-area SFCBs did not yield improved axial bending performance for the columns. In addition, a theoretical model was developed to predict the failure modes and capacities of columns reinforced with SFCB longitudinal reinforcement combined with CFRP-MF stirrup columns. This model exhibited a relatively high level of accuracy, underscoring its potential as a valuable tool for guiding the design of corrosion-resistant marine infrastructure and informing hybrid reinforcement schemes.