Structural performance and design of stainless steel SHS-concrete‑carbon steel CHS double-skin stub columns

Abstract

Concrete-filled double-skin steel tube (CFDST) with outer stainless steel square hollow section (SHS) and inner carbon steel circular hollow section (CHS) is introduced in this paper. The square-shaped section provides easier connection with other structural elements and the utilization of the three different materials (stainless steel, concrete and carbon steel) contributes to the advantages of their combined strength, corrosion resistance and economy. This paper reports a finite element (FE) analysis and the FE models are developed with consideration of geometric imperfection and stainless steel's non-linear material property. To validate the models, a comparison of the results of FE models and experiments is performed on the basis of ultimate section capacities, load deformation histories and failure modes. Parametric study is then carried out for the analysis of structural performance of CFDST stub columns, especially on interaction stresses between concrete and steel tubes, load deformation histories and stress distribution of each component. The failure modes and their corresponding ultimate limit states have been thoroughly discussed for the four typical types of CFDST stub column. In addition, the current international design codes including Eurocode 4, AISC and AIC are assessed with the generated ultimate section capacities from FE models. It is observed that ACI provides better predictions as compared to other codes. At last, the new design equation is proposed to predict the ultimate section capacity of the CFDST stub column which shows very good agreement with the FE analysis results.