Behaviour of CFRP externally-reinforced circular CFST members under combined tension and bending

• Longitudinal CFRP is efficient in increasing tensile strength of a CFST member.
• The CFST reinforced by ± 45° CFRP has the largest deformation capacity.
• A FE model was developed for reinforced CFST under combined tension and bending.
• The influence of the CFRP jacket on the interaction is very moderate.
• A simplified model was proposed for strength prediction.

This paper investigates the performance of circular concrete-filled steel tubes (CFST) externally reinforced by carbon fibre reinforced polymer (CFRP) sheets under the combined actions of tension and bending. The strengthening effect of CFRP layers was examined through tensile tests of 19 CFST specimens. The main experimental parameters include fibre orientation, load eccentricity, number of CFRP layers and anchorage system of CFRP sheets. A finite element analysis (FEA) model was developed to conduct mechanism analysis and parametric analysis of the composite members investigated. In general, CFRP with fibres oriented in the longitudinal direction is very efficient in increasing the strength of the CFST member. On the other hand, a wrapped CFST member strengthened at ± 45° angles to the longitudinal axis has the largest deformation capacity. Finally, a simplified strength model was proposed to predict the load-carrying capacity of CFRP-reinforced CFST members under combined tension and bending.