Behavior of circular bimetallic tube-confined concrete stubs under eccentric compression

This paper aims to investigate the behavior of eccentrically loaded circular stainless steel-carbon steel bimetallic tube-confined concrete stub columns. 15 stub columns including bimetallic tube-confined concrete with and without bars, and concrete filled bimetallic tube were prepared and tested. The results show that the difference in the failure patterns results from the different tube steel ratio of the specimens, even the total steel ratio of the specimens is similar. The ductility of the bimetallic tube-confined concrete is better than that of the concrete filled bimetallic tube with the same parameters. Under the condition of eccentric loading, the performance of the bimetallic tube-confined concrete stub column is lower than those of the concrete filled bimetallic tube with the same parameters. The stainless steel-carbon steel bimetallic tube has a good confinement effect on the core concrete. The strengthening performance of stainless steel can effectively improve the bearing capacity of the stub in the later stage, making up for the bearing capacity reduction of the specimen caused by concrete crash. The results calculated by the traditional code formula for steel tube-confined concrete are more conservative than the test results. The difference between the test results and the calculated results increases with the decrease of diameter-thickness ratio.