Research On Mechanical Properties Of Concrete Filled Steel Tube Under Axial Tension And Partial Tension

The concrete-filled steel tube(CFST)structure has been widely used in practical engineering due to its excellent combination performance,attracting scholars to study its various aspects of performance.Due to the low tensile capacity of the core concrete material of CFST components,most of them are used for compression members and the research on its compression performance is also the most extensive.On the contrary,there are relatively few studies on its tensile performance.However,in actual engineering,CFST members bear tensile loads from time to time.Therefore,it is necessary to systematically analyze and study the tensile performance of CFST members.In this paper,a combination of experiment and theory is used to deeply study the mechanical properties of CFST members under axial tension and eccentric tension.Mainly carried out the following work:(1)In this paper,5 specimens of concrete-filled steel tube and 1 specimen of pure steel tube were tested in axial tension.Analyze the failure mode of the specimen and the measured data curve,and conduct parameter analysis.The results show that:because the core concrete of the CFST member restricts the circumferential shrinkage of the outer steel pipe,the yield strength of the outer steel pipe is increased,resulting in an increase in the bearing capacity of the CFST member compared to the pure steel pipe specimen.(2)The finite element analysis method is used to model and calculate the axial tension test piece.At the same time,based on the secondary plastic flow model,a new steel constitutive relationship model suitable for CFST axial tension specimens is proposed,and the accuracy of the new model is verified.The final simulation results are in good agreement with the test results.(3)On the basis of the verification of the finite element model,the mechanism analysis of axial tension and eccentric tension members is carried out,and the stress distribution of steel pipe and concrete during the whole process of force is mainly analyzed,as well as the bearing ratio of steel and concrete.At the same time,the parameters of axial tension and eccentric tension members are analyzed,and the influence of steel content,steel yield strength,concrete strength and eccentricity on the bearing capacity of specimens is studied.(4)Through a large number of finite element calculations,a new simplified calculation formula for the axial tensile bearing capacity of concrete-filled steel tubes related to the ratio of wall thickness to diameter is suggested,and the accuracy of the formula is verified to provide a quick calculation for the bearing capacity of such members in engineering practice.reference.