A unified equation for strength design of concrete-filled steel tubular stub columns

This paper presents the development of a unified equation for the strength design of concrete-filled steel tubular (CFST) stub columns. An experimental database containing 922 tests on CFST stub columns with circular, square, rectangular and elliptical cross sections was first compiled. Finite element (FE) models were then developed for different CFST stub columns and validated against the corresponding test results. Following the successful validation, 749 FE models were generated for parametric studies, as a supplement to the test results. The test and FE results were used to investigate the strength enhancement index of the CFST stub columns and evaluate the strength predictions from current design codes. Overall, it was found that the strength predictions from design codes (AISC 360 and EN 1994-1-1) are generally conservative. A unified equation was proposed for predicting the ultimate compressive strength of CFST stub columns with circular, square, rectangular and elliptical cross sections. Generally, the proposed equation provides more accurate and consistent predictions than current design codes. The proposed unified equation is applicable to CFST stub columns with yield strengths of steel tubes up to 1000 MPa and compressive strengths of concrete up to 100 MPa.