Plasticity-based model for circular concrete columns confined with fibre-composite sheets

This paper presents analytical stress–strain curves that describe the axial and the lateral behaviour of externally and internally confined concrete in circular columns. The solution to the problem of an elastic cylinder confined by internal and external elastic confining materials is derived. Following the elastic solution, the analytical curves are derived based on the full elastoplastic behaviour of the confined concrete column and by using the well-known Drucker–Prager failure criterion to represent concrete behaviour. Application of the Drucker–Prager model does not require an iterative procedure in order to solve the problem and thus an explicit solution is obtained. The proposed model can be applied to describe the behavior of concrete confined by transverse steel reinforcement, by fibre-reinforced polymer (FRP) composites, or by both transverse steel reinforcement and FRP composites. It is shown that the analytical results are in good agreement with both experimental and the finite element method results.