Research On The Behavior Of Concrete-filled Steel Tubular Column And Steel Beam Joint With Outer Stiffened Ring

Concrete filled steel tubular structure is a type of new structure that can use the advantage of steel and concrete. Owing to its good behavior, the new structure is used more and more widely. Along with widely spread use of CFST (concrete-filled steel tube) structure, people have paid more attention to the design of CFST joint. Many foreign and domestic scholars process massive research on CFST joint. The research on the joints between the concrete filled square steel tube columns and H shape steel beams mainly focus on the inner stiffened Joints at present, but there are little theory and test research on the joints with outer stiffened ring.In order to research the hysteretic behavior, ductility, degradation of strength and stiffness, ability of energy dissipation, failure mechanism and characteristics of joints, four joints with outer stiffened ring between the steel tube columns and H shape steel beams were designed and tested under the low cycle reverse load. The parameter include the axial compression ratio and the linear stiffness ratio of steel beam's to column's. The 3D solid finite element models were built by the dimension of the CFST specimens, and the nonlinear finite element analysis was done using software ABAQUS. The results of finite element analysis coincide to the results of the experiments.The tests and the finite element analysis indicate that this kind of joint has plump hysteretic loop and good ductility. The plastic hinges of the connections with outer stiffened ring appear on the section of the beam between the ring and beam. The shear force is bear by the steel tube wall and the concrete together at the panel zone; Some of the moment is transformed from beam flange to the column web and the concrete at the panel zone by the outer stiffened ring connected to the column web, the remain is transformed to the column flange and the concrete at the panel zone by the inboard ring near the column corner. Based on test and theoretical analysis and the relative code, the equation of the joints bending resistant and shear resistant, strong columns and weak beams, strong joints and weak members are deduced, and the design suggestion of the joints are also given.