Research On Mechanical Behavior Of Concrete-filled Steel Tubular Corner Joints With Core Steel Tube Under The Horizontal Loads

The concrete filled steel tubular (CFST) has been used in the high building structure. However the CFST joint is one of critical technical issue in the CFST structure. Especially the CFST joint connected RC-beam and CFST column still have a lot of questions. The study on the joint will contribute to the structure design and engineering application. The semi-connected comer joint with core steel tube is presented by Prof Wang Yi Hong, which connects concrete filled steel tubular (CFST) column with RC beams. The mechanical behavior of the corner joint under horizontal loads is studied in the paper. Out steel tube of that joint is broken off in the directions connected with the beams and it is compensated for the remaining out steel tube by setting the core steel tube and stirrup, the outer steel tube is kept connecting in other side without the beam, the longitudinal bars in the beams pass through the joint, and the beam, the column and the joint is monolithically cast in the region of joint. Utilizing the finite element analysis (FEM) ANSYS, nine semi-connected corner joints with core steel tube was analyzed under the horizontal loads. The mechanical behavior of nine joints was studied by changing the diameter of stirrup, the yield strength of core steel tube, the strength of out concrete and the diameter of core steel tube. The cell's relation, the constitutive relation of material, the yield criterion and the boundary condition of the joint member were confirmed. The law of the stress layout in the member of the joint, the feature of the hysteretic curve and skeleton curve and the ductility was studied.The study shows that the hysteretic curves were full the ductility is good. The diameter of stirrup is increased, but the bearing capacity increased limitedly. under horizontal low cyclic repeated loading, the strength and stiffness of the joint is improved by increasing the strength of the core steel tube. The result of FEM shows that the ductility of the beam side is more than the one's of non-beam. When the diameter of the core steel tube reduce under the size of joints is confirmed, the ultimate capacity of the joint reduce, the bearing capacity of the core steel tube is play the role for the bearing capacity of the joint.