Experimental study and finite element analysis on mechanical properties of dumbbell-shaped concrete-filled steel tubular columns under combined compression-bending-torsion loading
With the axial pressure ratio(n)and the bending-torsion ratio(γ)as varied parameters,the tests of 4 circular-shaped and 4 dumbbell-shaped concrete-filled steel tubular members under combined compression-bending-torsion loading were carried out,the change rules of the torque-torsion angle curve,torque-shear strain curve and failure mode of each members with the parameters of the different axial pressure ratio and bending-torsion ratio were analyzed.The results show that in the case of the constant value of the axial pressure ratio,when the bending-torsion ratio is large,the member is mainly subjected to bending,and the failure mode is close to flexural feature.When the bending-torsion ratio is small,the member is mainly twisted around the center of the member,and the failure mode is approaching torsional feature.The ultimate torque increases with the increase of the axial pressure ratio.In the case of γ=2.80,when the axial pressure ratio increases from 0.00 to 0.11,the ultimate torque of the circular-shaped and dumbbell-shaped concrete-filled steel tubular members increases by 23％and 53％respectively,and when the axial pressure ratio increases to 0.22,the ultimate torque of circular-shaped and dumbbell-shaped concrete-filled steel tubular members increases by 23％and 99％respectively.The ultimate torque decreases with the increase of the bending-torsional ratio,and when the bending-torsion ratio increases from 0.90 to 2.80,the ultimate torque of circular-shaped and dumbbell-shaped concrete-filled steel tubular members decreases by 46％and 51％respectively.Through the finite element software ABAQUS,the relation curve of the torque-torsion angle curve and failure mode of the members during the whole process were analyzed.The calculation results by finite element are in good agreement with the experimental results.
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