Research On Mechanical Behavior Of Concrete Filled Steel Tube Columns Under Combined Bending And Torsion

Under gravity and the horizontal earthquake load,the combined effect of eccentric compression load and torsion will be produced in the piers of curved girder bridges and the main arch of arch bridge.In this paper,the torsion behavior of concrete filled steel tube under complex loading and the numerical simulation method were studied.The main research works are as follows:(1)In order to study the torsion behavior of concrete filled steel tube columns subjected to eccentric compression load,quasi-static tests were carried out on six specimens of concrete filled steel tube column subjected to static pure torsion,cyclic pure torsion and eccentric compression-cyclic torsion.The failure process,failure mode,torsional mechanism and hysteretic rules of concrete filled steel tubewere investigated.(2)The simulation method of steel and concrete material under hysteretic loading in the finite element program ABAQUS and the difference between monotonic load and hysteretic load were studied.We found a method for defining the performance of steel and concrete in concrete filled steel tubes.Based on that,we established a applicable and feasible finite element model of specimens under pure torsion and eccentric compression-torsion.(3)The parametric analysis was also carried out using the finite element model.The key factors affecting the stiffness and torsional bearing capacity and the torsional failure mechanism of concrete filled steel tube were found.The formulas for calculating the torsional stiffness and the torsional bearing capacity under monotonic loading were presented.Finally,the simplified calculation method of torque versus torsion angle hysteretic curve under cyclic loading was studied.(4)The effect about bending moment on torsional capacity of concrete filled steel tube was studied,and the relationship between torsional bearing capacity and bending moment under different parameters was discussed.The simplified calculation method of torsional bearing capacity was obtained by parametric statistics.