Axial compressive performance of circular CFST columns partially wrapped by carbon FRP

Abstract

To explore the axial compression property and failure mechanism of concrete-filled steel tubular (CFST) columns partially wrapped by carbon-fibre-reinforced polymer (FRP), a series of tests using carbon-FRP-strengthened circular CFST stubs and slender columns imposed with axial loads were conducted. The effects of various parameters including steel yield stress, number of carbon-FRP layer, slenderness ratio of the composite column, and spacing of carbon-FRP strip on the axial load bearing capacities of the tested specimens were studied. Moreover, the axial compression behaviour of the circular CFST columns with carbon-FRP composites was evaluated in terms of axial compression force (N)–longitudinal shortening displacement (δ) curves, axial stiffness, strain response, strength enhancement indexes, and ductility indexes. Subsequently, a nonlinear finite element (FE) analysis modelling concerning the surface contact action of carbon-FRP-strengthened circular CFST columns was established and validated experimentally. The experimental and analytical results indicate that strengthening the circular CFST stub columns using carbon-FRP wraps could improve their axial load bearing capacities and prevent outward local bulges for the thin-walled steel tubes. Only a slight effect was observed when laterally confined carbon-FRP strips were used for the type of slender composite columns. Finally, several simplified empirical formulas for predicting the axial load bearing capacity of the circular CFST column partially wrapped by carbon-FRP are proposed.