The Study On Joint Performance Of Steel-Concrete Composite Beam To CFT Column

In recent several decade years, CFT (concrete-filled tube) structure has been popularly applied in variety fields of engineering. In high and high-rise building construction, because the CFT column has special formation, the study on beam to column joint have been carried out all over the world. Today there are more than twenty joints have been applied in practical, and these joints are assumed as pinned or rigid in frame analysis. Need to attach importance to the rationality and the effect on frame analysis of these assumptions. There have been a great number of researches on CFT joints. But most of them focused on the ultimate resistance of certain joints. And the study on the stiffness of CFT joints has been seen seldom. As a matter of fact, the influence of joint's stiffness on the whole structure can hardly been neglected.As a part of National Natural Science Foundation of China "the study on restraining stiffness of joints of CFT frame", this paper focused on the study of steel-concrete composite beam to column joints of CFT. The type of joint had been recommended by the code CECS28:90.The four specimens were tested by monotonic loading, repeated loading and iterative loading. Steel tube was (?)159 X 5, steel beam was HN200 and HN150, thickness of concrete slab was 120mm, Steel tube and concrete slab were filled with C30 concrete. Studs were shear connectors between concrete slab and steel flange. The finite element model of the CFT joint was analyzed by the finite element package ABAQUS, and the results of four specimens as compared with the finite-element analysis for the verification for the model. Base on the models, changed its detail dimension to confirm the influence of each factor on joint stiffness.The paper put forward a joint, which was steel-concrete composite beam to CFT. The joint which studied on the stiffness is seldom in our country and is innovative. In area of negative moment, there was no obvious stress concentration in the top flange of composite beam. Elastic natural axis and plastic natural axis were close to top flange. The joint was damaged by lower flange compressive yielding. Concrete slab was tensioned, and complex situation was researched deeply. The plane cross-section was applied in design of the joint and in finite element analysis. The steel beam and concrete slab were assumed perfect bonding by studs, and no slip occurs. Finite element analysis fit for the tests. The study on the joint is propitious to study of frame joints and design of composite beam to column, and it is practicable sense.