Residual Bond Strength between Steel Tube and outside Concrete after Heating

The bond strength between steel tube and concrete is the foundation to ensure the good mechanical properties of concrete-encased concrete-filled steel tubular (CFST) columns. At present, there is little research on the residual bond strength between steel tube and outside concrete after high temperature cooling. The effect of heating and cooling on the residual bond strength between the steel tube and outside concrete is investigated in this paper. A total of ten specimens, including one unheated specimen and nine heating and cooling specimens, were tested to investigate the residual bond strength of steel tube and outside concrete. Test parameters include heating temperature and stirrup ratio. The test results showed that: (a) the bond failure load decreased gradually after high temperature with the increase of high temperature or the decrease of reinforced concrete stirrup ratio; (b) the bond failure load of push-out test was higher than that of push-back test after the same temperature; (c) the relative slip value between the steel tube and outside concrete decreased with the increase of the temperature; (d) the relative slip value had an increasing trend with the increase of stirrups ratio, but the influence was small.