Numerical study and design recommendation on eccentric compression behavior of FRP confined rectangular high-strength concrete-filled steel tubular columns

This paper presents a numerical study on the eccentric compression behavior of fiber reinforced polymer (FRP) confined rectangular high-strength concrete-filled steel tubular (CFST) columns. A refined finite element (FE) model of FRP confined CFST (FRP-CFST) column was developed and validated against the experimental results, including failure modes and load-displacement relationships. A parametric analysis was further conducted to investigate the influence of steel yield strength, concrete strength, corner radius, width-to-thickness ratio, number of FRP layers, partial wrapping scheme, eccentricity and FRP orientation on the eccentric compression performance and FRP improvement effect. The results indicate that increasing the number of FRP layers is an effective way to enhance the bearing capacity and ductility. A larger corner radius contributes to greater confinement efficiency by reducing stress concentration, but the corner radius-to-width ratio should be less than 1/6 to avoid the loss in bearing area. Appropriately spaced FRP strips can be utilized to reduce costs, but the wrapping proportion should not fall below 1/3 to ensure sufficient confinement effectiveness. Transverse FRP is more effective under small eccentricity, while longitudinal FRP improvement becomes dominant as eccentricity increases. Therefore, a hybrid scheme combining transverse and longitudinal FRP is recommended for eccentricity ratio greater than 2. Furthermore, two N-M interaction models were proposed and verified to predict the eccentric bearing capacity, with the plastic stress distribution model yielding more accurate predictions. The findings can provide valuable design recommendations for FRP-CFST columns in practical engineering applications.