Analysis on Behavior of Square RC Columns Strengthened with Concrete Filled Steel Tube Under Axial Load

The behavior of 1 referenced RC column and 9 RC columns strengthened with concrete filled steel tube under axial load were tested. The experimental results show that the bearing capacity of RC column increases by 3.65~5.39 times on average after strengthened. Moreover, the strengthened columns behave in a relatively ductile manner, and the applied load maintains at a certain loading level after the ultimate load. Based on the test data, 3-D finite element models established by ANSYS were applied to analyze the behavior of the specimens under axial load. Appropriate material stress-strain relations and failure criteria were considered. The ultimate loads and load-longitudinal deformation curves of test specimens were calculated and compared with the experimental results. It is found from the comparison that the calculation value agrees well with the experimental value, and the maximum error of calculated strengths is 5%.Additionally, the stress distributions of test specimens under the axial loading were analyzed by the verified models. The analysis results show that the load ratio of each component is unchanged at the initial stage of loading. As the load continues to increase, the steel tube shows obvious confinement on the RC column and post-cast strengthening concrete so that their peak stress significantly exceeds the uniaxial compressive strength. Therefore, the load proportion of steel tube decreases slightly, while the proportion of the concrete bearing load increases slightly. When the specimen reaches the ultimate load, the proportion of the steel tube bearing load increases due to the hardening of the steel tube and the crushing of the concrete. © 2022, The Editorial Board of Journal of Basic Science and Engineering. All right reserved.