Bond-slip behaviors of composite steel-reinforced high strength lightweight aggregate concrete columns with innovative X-shaped steel sections

This paper provides an insight into the bond-slip performance of the new type of steel-reinforced high strength lightweight aggregate concrete (SRLWAC) column with innovative X-shaped steel sections through experimental and theoretical studies. Three SRLWAC specimens were tested under push-out force; the variables are the confinement by stirrups (rho(sv)) and shear connectors (SCs). Force-slip curves, force axial and horizontal deformations, failure modes, and crack patterns of the specimens were investigated; the force transfer, bond-stress, bond shear transmission length, and strains were studied. Comparisons between the bond strength of the studied specimens and ordinary types column specimens from 13 previous studies showed a superior bond capacity for the new type specimens. Five related models of bond capacity were discussed, and the utility of the models was put forward. A simplified load-slip model was proposed and verified. The most feasible model and the simplified model were used in the parametric study. The results showed that the material strengths and geometric configurations parameters affect the bond strength capacity. The confinement and SCs have effects on the bond and failure mode. The natural bond-stress combined with SCs produced smaller bond strength than that from both natural bonds and using higher rho(sv). Recommendations for future works are developed.