Performance of circular bimetallic tube confined concrete slender columns under eccentric compression

This paper aims to investigate the performance of thin-walled circular stainless steel-carbon steel bimetallic tube confined concrete slender columns under eccentric compression. 14 slender columns including bimetallic tube confined concrete (BTCC) with and without rebar, and concrete-filled bimetallic tube (CFBT) were tested. A parametric analysis is conducted based on the validated finite-element model. The results show that the two steel tube layers worked well together and the thin-walled BTCC specimens behaved in a ductile manner. Under the same parameters, the decrease of the diameter–thickness ratio of bimetallic tube improves the bearing capacity and rigidity of the BTCC slender column, but reduces its ductility in the descending stage. The confinement effect of bimetallic tube on the concrete in BTCC columns is stronger than that in CFBT columns. When the yield strength of stainless steel and carbon steel is similar, the stainless steel–total steel ratio has little effect on the capacity of the column. Provided meeting the requirements of corrosion resistance, relatively thinner stainless steel tube is preferred to reduce the cost. The comparison between the simulation and the calculation results shows that the current design method can predict the bearing capacity of the BTCC slender column with large diameter–thickness ratio.