Analysis of dumbbell-shaped CFST members subjected to combined compression and torsion loadings

In a study examining the mechanical behavior of dumbbell-shaped concrete-filled steel tubes (CFST) under combined compression and torsion, four concrete-filled steel tubes were fabricated and tested. The test results revealed that after the completion of loading, the specimens exhibited significant torsional deformation but no apparent signs of damage, allowing them to continue loading in subsequent stages.The dumbbell-shaped CFST model was analyzed using the finite element method, and the accuracy of the finite element results was confirmed by comparing them with the existing test results. Based on this, the impact of various factors on ultimate torque was investigated, including steel tube strength, concrete strength, axial compression ratio, slenderness ratio, and steel ratio. In conjunction with the analysis of finite element param -eters, a straightforward calculation formula for the compression-torsion correlation curve of dumbbell-shaped CFST was proposed.