Study of Circular Reactive Powder Concrete-filled Steel Tube Stub Columns under Axial Compression

As a fundamental mechanical problem in steel and concrete composite structures, the axial compressive behavior of reactive powder concrete (RPC)-filled steel tube stub columns has been a concern of scholars worldwide. At present, the analysis method of RPC-filled steel tube is based on nonlinear finite element method and equivalent uniaxial stress–strain analysis model, but the analysis process is complicated and cannot accurately describe the interaction between the steel tube and RPC. Thus, this study proposed a nonlinear analytical procedure to evaluate the mechanical properties of steel tube and RPC accurately at different compressing stages. The method was employed to predict the load–deformation curves of RPC-filled steel tube stub columns under axial compression. Compressing experiments were conducted on such columns, and the characteristic hoop coefficient was derived. Comparison analysis was performed to verify the accuracy and efficiency of the analytical procedure. Results demonstrate that the characteristic hoop coefficient is a critical value for assessing whether the steel tube yields when columns reach the ultimate bearing capacity. Columns with small hoop coefficient have good ductility, but the material utilization rate of the steel tube is not high. Columns with large hoop coefficient have weak ductility and residual deformation capacity. Moreover, columns with characteristic hoop coefficient can reach good ductility and high material utilization rate. The characteristic hoop coefficient determined by the test analysis in this study is approximately 1.3. The analytical results are generally in good agreement with the experimental results until the starting position of strain hardening or local plastic buckling. The proposed method provides a good prospect for optimizing the design of RPC-filled steel tube columns.