A calculation model for cracking load of PVC-CFRP tube-reinforced concrete column

The PVC-CFRP tube-reinforced concrete column (PCTRCC) overcomes the challenging connection issue between beam members and PVC-CFRP tube confined concrete columns. To study the crack development law of the PCTRCC under axial compression and determine a calculation model of cracking load, the axial compression tests are conducted for fourteen PCTRCCs and three RC comparison columns. The influences of stirrup form and stirrup ratio outside the core column, CFRP strips spacing and layers, concrete strength grade inside the core column, and diameter-to-width ratio on crack development law, cracking load, ultimate strain, and initial stiffness of the specimens are analyzed. The research results indicate that the "H"- shaped crack or "N"-shaped crack is formed when the specimens with octagonal stirrup or diamond stirrup are damaged, but the surface of the specimens with the square stirrup has only a diagonal crack. As the the CFRP strips spacing decreases or concrete strength grade, stirrup ratio, CFRP strips layers, diameter-to-width ratio increase, the crack development rate of the specimens is reduced, and the ultimate strain and bearing capacity are improved. Compared with square stirrup, the crack development rate of the specimens with octagonal stirrups or diamond stirrups are reduced, and the ultimate strain and bearing capacity increases. Finally, based on the experimental study, the effect of concrete strength grade on cracking load is considered, and the calculation model for cracking load is proposed.