Experimental Research on Long-Term Performance of Axially Loaded Steel- Tube-Confined CFST Short Columns Considering Temperature Effect

In order to explore the long-term performance of steel-tube-confined concrete-filled steel tube (TCFST) short columns under axial compression, 10 specimens of TCFST short columns and 2 specimens of concrete-filled steel tube (CFST) short columns were designed and loaded under sustained axial compression for 850 days. The main research parameters include the stress ratio of core concrete (0.35, 0.50 and 0.65), the ratio between inner and outer steel tubes (0.30, 1.25 and 2.23), and the temperature (20, 45 and 55 ℃). The effects of various parameters on the long-term deformation performance of specimens were compared and analysed. Axial compression tests were performed on 6 load-bearing specimens at room temperature, 6 load-bearing specimens subjected to the temperature action, as well as 4 load-free specimens for comparison, to investigate the influence of long-term loads and temperature effect on the axial compression bearing capacity. The results showed that the larger ratio between inner and outer steel tubes, the smaller stress ratio of core concrete, and the smaller temperature led to a long-term deformation of the TCFST. The combined effects of long-term loading and temperature had no significant effect on the initial stiffness and axial bearing capacity of the TCFST.