| The rectangular concrete-filled steel tubular (CFST) composite structures have the special properties,such as high-strength,good ductility,better seismic behavior, and convenient construction,etc. The bifurcate column together with double-cruciform connections of column to beam form the Dendriform Connection of concrete filled steel rectangular tubes.Firstly the experimental studies on four groups with six 1/2-proportional specimens are proceeded in this paper,the strain of steel tubes and beams under the monotonic and low-cycle repeated load are accurately measured,the hysterious curves are obtained and the load-displacement curves,degradations of strength and stiffness, ductility, failure mechanism as well as failure characteristics are analyzed.Secondly 3D nonlinear Finite Element Model is established by ANSYS a general finite element analysis software, which all nonlinear effects of material, geometry are considered. According to the results of finite element analysis, the contours of stress distribution of the steel tubes are given in this paper. The structural deformative shapes and stress states under the load effect can be clearly observed in these figures. The bearing mechanism behavior and failure mode of the Dendriform Connection are investigated.Through the researches, we can draw the main conclusions as follows:â‘ All the cyclic loops of the Dendriform Connection of CFST are nearly rectangular,and no or little pinch effects can be found. These loops indicate the good dissipation of energy;â‘¡The endurance of performance of joints increases while steel and concrete work together, but the Dendriform Connection has little effect on joints when the axial compressive ratio is not high;â‘¢The 3D models in this paper can nicely simulate the mechanical characteristics of this type of joints.Dendriform Connection of CFST which is a new type of joint is studied in order to provide references for relative engineering design.
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