Analytical modelling and design of partially CFRP-wrapped thin-walled circular NCFST stub columns under axial compression

Abstract

The partial CFRP (carbon fiber reinforced polymer) wrapping scheme is widely used for strengthening engineering practices to obtain a moderate improvement in strength, whereas detailed investigations on partially CFRP-wrapped thin-walled circular normal-strength concrete-filled steel tubular (NCFST) stub columns are seldom presented. This paper aims to conduct a series of numerical analyses to figure out the axial compressive performance of circular NCFST stub columns wrapped by CFRP belts partially. A nonlinear finite element (FE) modelling focused on the surface interaction as well as the CFRP and thin-walled hollow steel section (HSS) confinement effects on the concrete infill is developed via ABAQUS solver and the accuracy is validated against the existing experimental data. Following this, a systemic parametric investigation is developed to explore the impact of steel yield stress, concrete compressive strength, diameter: thickness ratio, CFRP wrapping ratio and number of CFRP layer, etc. on the axial compressive properties of the partially CFRP-wrapped thin-walled circular NCFST stub columns. Elaborate investigations on the surface contact action, stress-strain response, typical axial force versus axial shortening curve and failure modes are presented to better figure out the axial compressive behaviour of the type of composite column. A discussion on the effective wrapping scheme of the partially CFRP-wrapped thin-walled circular NCFST stub column imposed with axial compressive force is described as well. Finally, two types of design formulas in compliance with the unified theory and the tubed concrete method are proposed to assess the axial compressive resistance of the partially CFRP-wrapped thin-walled circular NCFST stub column. The research may provide a considerable and scientific basis for employing CFRP materials for the CFST structures. • The FE modelling of the partially CFRP-wrapped axially loaded thin-walled circular NCFST stub column was developed. • The failure modes, the contact stress, the stress-strain response and the effective wrapping scheme were explored. • Design formulas to predict the axial strength of partially CFRP-wrapped circular NCFST stub columns were proposed.