Behavior Of Round-Ended Concrete-Filled Steel Tubular Beam-Columns

Round-ended concrete-filled steel tubular(RCFST)columns have high bearing capacity,good seismic performance,easy construction,beautiful cross-section and high lateral rigidity.However,domestic and foreign scholars on the study of round-ended concrete-filled steel tubular columns is limited.The existing researches mainly focused on the mechanical properties of the stub columns under axial compression.Few researches on RCFST under the pure bending or eccentric compression can be found.In order to comprehensively achieve the mechanical properties of RCFST columns,it is necessary to study the mechanical properties of RCFST members under bending and eccentric compression.The main contents of this paper are divided into the following parts:(1)Reading the current literature,understanding the research status of related topics,and determining the necessity of thing research topic.(2)Six speimens under pure bending and twelve speimens under eccentric compression were carried out.The parameter of the bem test is the depth to width ratio.And the parameters of the RCFST columns include the eccentricity and slenderness ratio.The experimental results show that the failure mode of the RCFST beams is the in-plane bending failure.The failure mode of the RCFST columns under eccentric compression is the overall instability failure,and the member shows high bearing capacity and good ductility.(3)The finite element(FE)software ABAQUS was used for numerical simulation.A reasonable material constitutive relationship was adopted.The mechanism was analyzed by using the FE model.The stress distribution and the interaction between the steel tube and concrete were analyzed.The analysis shows that the confinement of the steel tube on the core concrete at the arc section is stronger than that at the straight section.(4)Based on the FE model,the parametric analysis of slender columns under axial compression,beams and eccentrically compressive columns was carried out respectively.The mian affecting factors are yield strength of steel,concrete strength,steel ratio and depth to width ratio.For slender columns under axial compression,the steel ratio has few effect on the stability coefficient,the concrete strength and depth to width ratio have a few influence,but the strength of steel has the most significant influence.For the beams,the calculation coefficient of flexural strength increases with the increase of yield strength and steel ratio,but decreases with the increase of concrete strength and depth to width ratio.For the member under eccentric compression,the equilibrium point of the related curve moves inward with the increase of the steel yield strength and steel ratio,and moves outwards with the increase of the concrete strength.The depth to width ratio has few influence.(5)Based on the results of parametric analysis,the formulas for the load carrying capacity of slender columns under axial compression,beams and beam-columns are proposed.