Numerical analysis and design calculation of foam concrete-filled cold-formed sorbite stainless steel built-up composite columns

To address premature local buckling and inadequate corrosion resistance in cold-formed steel built-up columns, a novel foam concrete-filled cold-formed sorbite stainless steel composite T-shaped column (FC-CSSS-T) has been proposed. To better understand the axial compressive performance and to recommend appropriate design methodologies for this new section, a comprehensive numerical parametric analysis was conducted taking basis of a series of test validations. The effects of some key parameters, such as foam concrete strength, steel thickness, and cross-sectional dimensions were quantified and discussed, and the results were used to exam the applicability of five existing design codes and two existing calculation methods. Results indicated that the foam concrete fillings effectively delayed the onset of local buckling of sorbite stainless steel, however, the confinement effect derived from infilled foam concrete was weaker than the conventional concrete-filled steel tube (CFST) columns, which resulting that the commonly used calculations on CFST could not be directly used for the proposed FC-CSSS-T in this article. Also, the calculations in ACI 318-05 seems quite conservative, but other codes and methods overestimated the ultimate strength of them by up to 50% because of the same reason. Therefore, a tailored design method for FC-CSSS-T columns was proposed with errors less than 5% by comparing the predicted results and the numerical/test results, which can be used for axial compressive design of the proposed new sections.