Investigation of the axial compressive behaviour of CFRP-confined circular CFST stub columns with inner latticed steel angles

Abstract

To investigate the compressive behaviour of carbon fibre-reinforced polymer (CFRP)-confined circular concrete-filled steel tube (CFST) stub columns with inner latticed steel angles, the axial compression test was carried out in this paper. The main parameters investigated included the diameter-to-thickness ratio of the outer steel tube, the cross-sectional area of the inner latticed steel angles and the number of CFRP layers. First, the failure modes, load-displacement curves, ultimate load results and load-strain curves were obtained experimentally. Second, the stress-strain curves of steel tubes, the confining stress on the concrete and the stress-strain curves of the concrete were analysed according to the experimental results. Finally, design equations for the ultimate load of CFRP-confined circular CFST stub columns with inner latticed steel angles were proposed. Research results showed that the latticed steel angles have an excellent effect for improving the ultimate load and ductility of CFSTs, and the CFRP have an obvious confining effect on the local buckling of steel tubes, thus improving the ultimate load of CFSTs with latticed steel angles. It can be concluded that the failure of CFRP-confined specimens were mainly due to the rupture of the CFRP caused by the local buckling of steel tubes, and the latticed steel angles could participate in the overall loading process and provide a certain confining effect on the concrete enclosed by the latticed steel angles. On the basis of experimental results, design equations for predicting the ultimate load of CFRP-confined CFST clumns with latticed steel angles were proposed and compared with experimental results, and conservative prediction results were acquired.