Refining bond–slip constitutive relationship between checkered steel tube and concrete

• The height of checkered pattern has been found to have a significant influence on ultimate average bond strength.
• The basic bond–slip constitutive model matches well with our test curves.
• The distribution regularities of checkered steel tube strain, bond strength and slippage of CFCST have been obtained.
• Two position functions are introduced to establish bond–slip constitutive relationship.

In view of the problem of low average bond strength between steel tube and concrete, nine push-out test specimens of concrete filled checkered steel tube (CFCST) have been done to investigate the bond performance between checked steel tube and concrete. According to the experimental results of bond–slip curves, a basic bond–slip constitutive model is established. Considering the varying influential parameters of height of checkered pattern and concrete strength, the changing trends of the ultimate average bond strength are analyzed. Meanwhile, the distribution regularities of checkered steel tube strains, bond strengths and slippages along the longitudinal length, and bond–slip curves in different longitudinal positions are obtained. Based on the basic bond–slip constitutive model, two position functions are introduced to establish the bond–slip constitutive relationship. The experimental results show that the height of checkered pattern has a significant influence on ultimate average bond strength and that the basic bond–slip constitutive model matches well with our test curves. The introduction of the position functions laid the foundation for further finite element analysis of CFCST.