This study experimentally investigates the interfacial bond behavior of concrete-filled steel tubes (CFST) under the combined effects of freeze-thaw cycles and ambient temperature. Key parameters, including the number of freeze-thaw cycles, ambient temperature, steel tube wall thickness, and core concrete strength, were examined to assess the failure modes, load-displacement curves, and strain distribution patterns of the specimens. The results indicate that the failure modes of the specimens after freeze-thaw cycles and ambient temperature exposure were generally consistent, with varying degrees of corrosion and fragmentation observed on the surfaces of the steel tube and concrete. The bond strength decreased significantly with increasing freeze-thaw cycles and temperature (after 200 freeze-thaw cycles, bond strength dropped by 49.32%, while a temperature rise from 20°C to 60°C led to a 7.14% reduction). Notably, The coupling effect of these factors resulted in a more pronounced decline (reaching 59.12%). Conversely, increasing the steel tube wall thickness or core concrete strength enhanced bond performance. Furthermore, based on experimental data, a bond strength calculation formula was established, and a bond-slip constitutive model for CFST in freeze-thaw environments was proposed by considering interfacial damage mechanisms. This study provides critical insights for the design of such structures in cold regions and areas with large temperature variations.

Freeze-thaw cycles；Ambient temperatures; Concrete-filled steel tube (CFST); Bond behavior； Constitutive model