Axial compressive behavior of seawater sea-sand coral aggregate concrete-filled circular FRP-steel composite tube columns

Abstract To better directly apply undisturbed seawater, sea sand and coral aggregates to ocean engineering, a new type of circular concrete-filled FRP-steel composite tube structure was designed. The core concrete is composed of sea sand as a fine aggregate, coral as a coarse aggregate and seawater as the mixing water. The FRP-steel composite tube is formed by wrapping FRP on the inner and outer walls of the steel tube. Thirty-six new circular seawater sea sand coral aggregate concrete (SSCC)-filled FRP-steel composite tube columns (SCCFCTs) were subjected to monotonic axial compression tests. The main test variables were the steel tube diameter-thickness ratio, FRP layers and FRP type. According to the different diameter-thickness ratios, the final failure mode of the specimen was divided into shear failure and extrusion expansion failure. The increase in the number of FRP layers and the decrease in the diameter-thickness ratio of the steel tube led to a significant improvement in the ultimate stress and strain of the specimens. When the other test parameters were kept the same, the CFRP-confined specimens had a higher ultimate strength and the BFRP-confined specimens had a slightly higher ultimate deformation capacity. Finally, the versatility of the existing model for the test data was evaluated and the complete stress–strain curve of the SCCFCTs under compression was simulated. The calculated results were satisfactory.