The external connectors effects on the bond strength of concrete filled square steel tube

External shearing connectors effectively improve the bond strength of concrete filled square steel tube (CFST), which ensures the concrete and steel tube work together properly. Based on the two CFST joint push-out tests, the influence of external connectors on the CFST bond strength was obtained. It is demonstrated that distribution of bond strength along specimen height is uneven. An increase in push-out load was due to the effect of "confinement", "clamp" and "hoist node". The bearing capacity equation of connectors is obtained based on literatures and experimental data. It is found that calculated results are in line with experimental data. Further attentions should be paid to this field.