Design of stainless steel CHS-concrete infill-carbon steel CHS double-skin stub columns

Abstract

Concrete filled double-skin tubular (CFDST) stub column with outer stainless steel circular hollow section (CHS) and inner carbon steel CHS is presented in this paper. It combines the strength of stainless steel, concrete and carbon steel, and also provides the stainless steel's durability, ductility and corrosion resistance properties along with the lighter weight due to the sectional feature. Finite element analysis (FEA) is done in this paper and the developed FE models are verified with the available test results on the basis of failure modes, full load-deformation curves and ultimate strengths of the specimens. Afterward, a series of parametric analysis are conducted to investigate the structural performance of each component and the overall column as well as the confining stresses between the tubes and concrete. In addition, the effect of stainless-steel grade, concrete strength, carbon-steel strength, diameter-to-thickness ratio of outer tube, diameter-to-thickness ratio of inner tube and hollow ratio on confining stress and mechanical property of sandwiched concrete is studied. The constitutive models of sandwiched concrete and outer stainless steel tube under plane stress are proposed. Based on these proposed models, the fiber element model is used to predict the mechanical properties of this composite column and then checked with the finite element modelling (FEM) outputs. Different design methods such as ACI code, European code, continuous strength method (CSM), Han et al. method and Nie et al. method are assessed to evaluate the applicability and accuracy. Finally, a new design method for calculating the ultimate bearing capacity of the CFDST stub column is proposed, which exhibits good agreement with the results of the FEA.