Performance of square high-strength steel concrete-filled steel tubes under long-term sustained axial tension

This is the authors' abstract. We don't add key points for this paper.

Long-term structural performance of concrete-filled steel tubular (CFST) structures are significantly influenced by the time-dependent behaviour of core concrete, including shrinkage and creep. However, limited attention has been paid to the effect of long-term sustained tension on square CFST members. This paper presents an experimental and numerical investigation into the axial tensile performance of square high-strength steel concrete-filled steel tubular (HSS-CFST) stub columns under sustained tension. A series of long-term sustained tensile loading tests were first conducted, followed by ultimate axial tensile tests. A finite element (FE) model was developed incorporating the effects of concrete shrinkage and creep. Using the validated model, the degradation mechanism of composite action between the steel tube and core concrete was analysed. The results reveal that sustained tensile loading induces stress redistribution, leading to a resistance reduction of square CFST columns, ranging from approximately 2–5%. A parametric study was conducted to evaluate the influence of key factors and a simplified design method for the long-term load coefficient is proposed, which provides predictions within ±2% error compared with experimental and FE results. The findings enhance the understanding of the long-term tensile behaviour of square HSS-CFST members and support the development of life-cycle design approaches for such composite structures.