Experimental study and finite element analysis on axial compression performance of CFRP-PVC confined coral seawater and sea-sand concrete columns

In this paper, a composite column using carbon fibre reinforced plastics and polyvinyl chloride composite tube (CFRP-PVC) to constrain coral aggregate seawater sea-sand concrete (CSSC) was proposed, and CFRP was pasted on the inner and outer walls of the PVC tube. To investigate the effects of the number of CFRP layers and void defects on the axial compression performance of PVC tubes, six specimens were made for axial compression loading tests and finite element parameter analysis. The results indicate that due to PVC improving the integrity of CFRP, PVC tube provide a stress transfer path for CFRP, placing CSSC in a triaxial compression state. When both the inner and outer walls of the tube are pasted with CFRP, brittle failure of CFRP-PVC tube can be effectively avoided and have relatively superior mechanical properties. In the same situation, when one layer of CFRP is pasted on the inner wall of the tube, it has better ductility and bearing capacity. When two layers of CFRP are pasted on the outer wall of the tube, the coefficient of constraint stress increase is as high as 121.5%, and the void defect only has a significant impact on ductility. A finite element model of CFRP-PVC confined CSSC columns considering Hashin damage criterion was established based on ABAQUS, accurately predicting the failure process and CFRP damage morphology of test columns under axial load. Parameter analysis shows that when the confinement coefficient of CFRP-PVC confined CSSC columns is less than 0.3 and the height-diameter ratio is greater than 15, the load-displacement curve will lose the strengthening stage, and increasing the number of outer CFRP layers will slightly increase the stiffness of the strengthening stage. A bearing capacity calculation method suitable for CFRP-PVC confined CSSC was proposed based on the model of steel tube confined concrete, with an error of 1.2%.