Experimental and numerical investigations of stainless steel tubular columns strengthened by CFRP composites

Abstract

This paper presents experimental and numerical investigations of cold-formed circular stainless steel tubular (HSST) stub columns strengthened externally using carbon fiber reinforced polymer (CFRP) wraps. For the experimental investigation, eleven stub columns were tested under axial compression loading. The experimental variables were the CFRP thickness (tf), the CFRP arrangement (fully or partial wrapping), and the diameter-to-thickness ratio of stainless steel tubes (D/ts). The ratio of the compressive strength of wrapped specimens to that of unwrapped specimens (strengthening ratio) was employed to assess the compressive behavior of CFRP-wrapped HSST columns. Three-dimensional finite element (FE) simulation was implemented using ABAQUS software and validated against the experimental results. A parametric study was performed on the validated FE models for further investigation. The experimental results indicated that the full CFRP wrapping reasonably enhanced the ultimate compressive strength of the columns. In contrast, the partial wrapping showed no improvement in the ultimate compressive strength. The FE parametric study results showed that the strengthening ratio (i) decreases with increasing the diameter of the tubes, (ii) decreases when the failure mode changes from outward to inward local buckling (iii) is affected by the strength of the CFRP and tube materials. Based on the parametric study results, a design model was proposed to predict the ultimate strength of axially loaded CFRP-wrapped HSST stub columns.