EXPERIMENTAL STUDY ON THE CREEP CHARACTERISTICS OF HIGH-STRENGTH CONCRETE FILLED HIGH-STRENGTH STEEL TUBE

High strength concrete filled steel tube (HS-CFST) is widely used in civil engineering, however, the studies on the creep properties of HS-CFST are rarely reported. It measured the shrinkage and creep of fifteen specimens with different steel ratios under the action of axial compression for 365 days. The experimental results were compared with the prediction ones from the creep prediction model of MC 90, ACI 209 and MC 2010. It showed that: the creep coefficients of HS-CFST specimens are far less than that of the plain concrete specimens, and by the end of 365 days, the creep coefficient of plain concrete was more than twice of that of concrete in HS-CFST. The steel ratio affects the creep of the CFST specimens. The creep coefficient decreases as the steel ratio increases. Among the three existing creep models, the MC 2010 model can well predict the creep behavior of the HS-CFST specimens. Furthermore, the creep coefficient of the HS-CFST specimens were also compared with that of the normal strength CFST, and the results showed that the creep of CFST decreases as the compressive strength of the core concrete increases. It provides a useful reference for the creep prediction and creep control of HS-CFST under the action of axial compression.