Test and theoretical investigation of an improved CFRP-steel tube composite member under axial compressive loading

Abstract

This paper presents an experimental and numerical study on the mechanical characteristics of an improved CFRP steel tube composite members (CFRP-STCMs) under axial compressive loading. The CFRP-STCM was reinforced with a thick-walled steel tube at both ends to prevent local buckling of CFRP retrofitted equal thickness circular steel tube under axial compressive load. The main focus of the lab test was the effects of fiber winding directions and the test results reveal that the related specimen mainly suffers from overall buckling failure modes. The remaining failure characteristics of the test specimens vary with the change in the fiber winding direction. The longitudinal fiber winding direction has the most obvious reinforcement effect on the load-bearing capacity of the composite member. The ±45° fiber winding direction leads to obvious torsion failure modes after the overall buckling of the test specimen. The numerical modeling was carefully validated using the test results and an extensive parametric analysis was conducted covering a reasonably wide range of geometric configurations. Parameterized numerical analysis reveals that the initial geometric imperfections (initial curvature) and the geometric configurations of the composite member other than the thickness of the adhesive layer have a significant influence on the load-bearing capacity of the composite member. A modified theoretical method for predicting the critical load of the composite member is proposed based on the Perry-Robert stability formula. The proposed simplified formula can accurately predict the critical buckling load of CFRP-STCM with errors and coefficients of variation are −2.71% and −0.014, respectively.