EFFECT OF VOID RATIO AND INNER TUBE GEOMETRY ON CFDST BENDING BEHAVIOR

Abstract

Concrete-filled steel tubes (CFST) and concrete-filled double steel tubes (CFDST) have proven to be excellent composite structural elements. However, available literature has not sufficiently addressed the bending performance of concrete-filled double steel tubes. The current study aims to explore the bending performance of CFDST numerically and compare it with its single-tube counterpart (CFST). The study was conducted using the commercial Abaqus software. Two variables were evaluated in the current study: the void ratio in the inner tube and the shape of the inner tube. The finite element model included an outer steel tube fixed at a size of (100×50×1.88 mm) across all samples, while the inner tube diameter varied between (20, 32, and 40 mm), and the cross-sectional shape of the inner section was changed to a circular form, another model to a rectangular form, and another to a square form. The results showed that using void ratios as a percentage of volume (7.11%, 28.2%, and 28.5%) led to an increase in bending resistance (11.27%, 11.08%, and 6.88%), respectively. Moreover, changing the shape of the inner tube to circular, rectangular, and square increased the bending resistance by 11.08%, 4.47%, and 0.91%, respectively. These results provide a deeper understanding of the bending behavior of CFDST composite tubes and help in optimizing the inner tube design for composite materials.