Axial compression performance of FRP-galvanized corrugated steel tube seawater sea-sand concrete columns

A new combined column of fiber reinforced polymer (FRP)- galvanized corrugated steel tube (CST)-seawater sea-sand concrete (SSC) were proposed in this paper. The structure was composed of inner seawater sea sand concrete, intermediate corrugated steel tubes, and outer FRP sheet. To investigate the axial compression performance of this new combined column, a total of fourteen specimens were prepared, with the main parameters being the number of FRP layers (0, 1, 2, 3) and FRP types (BFRP, CFRP). The test results show that the primary damage mode of the FRP-galvanized corrugated steel tube seawater sea-sand concrete columns is shear damage and local buckling damage, and increasing the number of FRP layers could improve the ultimate load and ultimate strain of the columns. The unique corrugated structure makes the steel tube only provide circumferential confinement and avoid axial load transfer, which plays a confinement role similar to a stirrup. Compared with the specimens without FRP confined, the ultimate load and ultimate strain of BFRP-confined specimens increase by 13.9%-15.8% and 16.2%-33.7%, respectively, and those of CFRP-confined specimens increase by 19.6%-28% and 14.5%-24.1%, respectively. The strength calculation model of the existing FRP-stirrup composite confined concrete is evaluated in conjunction with the test data. The existing FRP-stirrup composite confined concrete strength calculation model is evaluated in conjunction with the experimental data.