Research On Mechanical Behavior Of Dumbbell-Shaped Concrete-Filled Steel Tubular Under Combined Compression And Torsion

Dumbbell-shaped concrete-filled steel tube is a combination of welded steel webs between two sealed round steel tubes.This type of section is commonly used in bridge arch rib structures.The arch rib is under compression and torsion composite stress state due to external loads such as wind and earthquake.The theoretical study on the combined forces of compression and torsion of dumbbell concrete-filled steel tube has been put on the agenda gradually.Therefore,this dissertation from two aspects of test and theoretical study of dumbbell shaped steel tube concrete torsional force under the action of composite mechanical properties.Then,a simple calculation formula of the compressure-torsion correlation curve is proposed and the main contents of this study are drawn as follows:1.Taking the axial compression ratio(n)as the variable parameter,the experimental study on four dumbbell shaped concrete filled steel tubular members under the condition of compression and torsion was carried out,and the load displacement curve,load rotation curve and load shear strain curve were obtained.There was no declining section in each curve,and the curve showed a stable upward trend in the later period.2.The large-scale general-purpose finite element software was used to calculate the dumbbell-shaped concrete-filled steel tube model.The correctness of the finite element results was verified by the existing test results.Based on this,the dumbbell-shaped concrete-filled steel tube was also tested under compression and torsion.The entire process of torque-rotation angle is analyzed.At the same time,the finite element analysis of the influence of five parameters of steel tube strength,concrete strength,axial compression ratio,slenderness ratio and steel content on the torsional capacity of dumbbell-shaped concrete-filled steel tube models.3.The compression-torsion correlation curve T/T _u-N/N_u of dumbbell-shaped concrete-filled steel tube is proposed.The results show that the four main parameters of steel tube strength,concrete strength,axial compression ratio and steel content ratio have no significant effect on the compression-torsion correlation curve.The abscissa of the torsional correlation curve is reduced,and then a simplified calculation formula for the compression-torsion correlation curve is proposed.The simplified calculation formula is compared with the experimental and finite element results,and the results agree well.