Self-weight buckling of FRP tubes filled with wet concrete

The high strength-to-weight ratio and corrosion resistance of fibre-reinforced plastic (FRP) composites coupled with reduced cost have made them an attractive option for retrofitting old structures and for new construction. In a number of recent studies, concrete-filled FRP tubes have been proposed to replace concrete-filled steel tubes as columns. A possible failure mode of these columns, which has never been pointed out before, is that the tube may buckle under the weight of the wet concrete during construction, owing to their low elastic modulus-to-strength ratio, particularly for glass-fibre-reinforced plastic (GFRP) tubes. The main purpose of this paper is to demonstrate the likeliness of this failure mode in real concrete-filled GFRP tubular columns. To this end, results of experiments conducted on plastic tubes filled with cement slurry are presented. The experimental loads are compared with, and found to match closely, theoretical predictions of a cantilever column under a uniformly distributed axial load. The theoretical formula is then used to establish the likeliness of this failure mode in real columns.