Behaviour of concrete-filled steel-tube columns strengthened with high-strength CFRP textile grid-reinforced high-ductility engineered cementitious composites

Abstract

In this study, a new strengthening technique was developed to improve the mechanical behaviour, fire resistance, and corrosion resistance of concrete-filled steel tubes (CFSTs). The proposed technique involved the strengthening of CFST columns using high-strength carbon fibre-reinforced polymer (CFRP) textile grid-reinforced high-ductility engineered cementitious composite (ECC). The behaviour of composite columns under axial compression was investigated. A total of 30 specimens, which comprised 27 strengthened columns and three un-strengthened control specimens, were subjected to experimental tests. The parameters considered for the tests were the number of CFRP textile grid layers, diameter–thickness ratio, and concrete strength. The experimental results showed that strengthened specimens exhibited a better strengthening effect than the control specimens. Unlike brittle failure, which occurred when the CFST columns were strengthened with FRP sheets, the ductility of the columns strengthened with CFRP textile grid-reinforced ECC was as good as that of CFSTs because of the occurrence of progressive failure. The in-filled concrete, whose strength increased owing to the confinement of the CFRP textile grids, resisted most of the loads on the strengthened columns. Based on different models, equations were derived to predict the load-bearing capacity, and the predicted results showed high accuracy.