Abstract: In order to reveal the interfacial bond behavior between a circle steel tube and concrete after exposure to elevated temperatures and water cooling, a total of 23 concrete-filled circle steel tube specimens subjected to high temperatures and water cooling were designed for push out test, by considering parameters such as concrete strength grade, anchorage length, cooling method and maximum temperature. The apparent change after cooling and the failure mode during loading were observed respectively. The load-slip curves and characteristic parameters were obtained. Factors affecting the interfacial bond strength were analyzed. The bond strength expression and bond- slip constitutive equation were proposed. The results showed that the interfacial bond strength increases first and then decreases with the increase of the maximum temperature; The bond strength is inversely proportional to the anchorage length, and the higher the maximum temperature is, the more obvious the relationship is; The bond strength of the specimens subjected to water-cooling is lower than that subjected to natural cooling, and the higher the maximum temperature is, the more significant the difference is.

Key words: fire；high temperature test, concrete- filled circle steel tube, water cooling, bond behavior, constitutive equation