Analysis of CFRP-confined CFST columns reinforced with steel angles under axial compression

To study the axial compression properties of specimens of concrete-filled steel tubes reinforced with steel angles, abbreviated as SRCFST, and of specimens of FRP-confined SRCFST, abbreviated as F-SRCFST, relevant finite element (FE) models were established using ABAQUS software. For verifying the accuracy of the proposed FE models, the axial load carried by each component of the specimen was first analysed and the distribution rules of the contact pressure between the steel tube and concrete as well as between the steel angles and concrete were analysed. In the second phase, the important parameters, such as the yield strength and wall thickness of the steel tube, the yield strength and cross-sectional area of the steel angles, the tensile strength and number of FRP wrapping layers were analysed. The third phase consisted of creating and proposing the design formulas for the SRCFST and F-SRCFST specimens on the basis of parametric analyses and numerical fitting method. The research results indicate that FRP has a minimal effect on the axial carrying capacity of the steel tube and the fundamental effect for the improved ultimate load is the indirect confinement effect by the FRP on the concrete. The proposed design formulas can accurately predict the ultimate load of SRCFST and F-SRCFST specimens, and the calculation error is generally within 10%.