Push-out test of pre-stressing concrete filled circular steel tube columns by means of expansive cement

The expansion/shrinkage behaviors and bond carrying capacities of 17 short, pre-stressing concrete filled circular steel tube (PCFST) columns by means of expansive cement and three short, conventional concrete filled circular steel tube (CFST) columns are experimentally investigated. The results indicate that both concrete mixes and dimensions of the steel tube have important influence on expansive behaviors of PCFST specimens. The pre-stress in concrete core is a sensitive parameter to the bond strength as well as the load–slip relationship. The current work also indicates that PCFST columns have much higher bond strength than CFST columns and this recommends a new method to improve the bond strength of composite structures. Finally, an empirical equation for predicting the bond strengths of PCFST columns is proposed.