Study of bond-slip push-out test of circular hollow steel tube and UHTCC

In this study, the influence of the slenderness and diameter-thickness ratio on the interfacial bonding performance of hollow steel tube and Ultra-high toughness cementitious composite (UHTCC) was analysed by conducting push-out test. The study examined the specimens' failure modes, strain distribution curves along the longitudinal direction of the steel tube, load-slip behaviour, and interfacial bonding mechanisms. A finite element model was developed and validated against experimental findings. The results indicated that neither the hollow steel tube nor the UHTCC reached their respective yield strengths during testing. The strain on the inner surface of the steel tube increased with increasing load. The interface load-slip curve revealed distinct cementation, slip, and friction phases. The stress distribution and load-slip characteristics of the steel tube simulated via finite element analysis closely match the experimental outcomes. Subsequently, considering the influence of the steel tube length and diameter, a statistical regression analysis was performed to determine the bond strength and bond failure load of the hollow steel tube and UHTCC, yielding calculation formulas correlating these parameters with the slenderness and thickness ratios. An error analysis validated the derived formulas against experimental and simulation results. Furthermore, two variables, namely the shear modulus of the bonding layer and the wall thickness of steel tubes, were introduced for the finite-element simulation under linear elastic conditions, and the changes in the related properties of the hollow steel tube and UHTCC members in response to the variation of some factors were discussed and analysed.