Nodes Mechanical Properties Of Steel - Concrete Composite Frame Research

Steel-concrete composite frame structures, which combine the best features of both steel and concrete structures, have become one important new direction of development of structural systems in recent years. In the design and calculation of the steel-concrete composite frame structure, the design and calculation of joint is one of the key issues. However, the current experimental study and theoretical analysis of the joint lagged behind the practice. Therefore, based on the research status and existing problems of the steel-concrete composite frame structure joint, this thesis will study the steel-concrete composite frame structure joint in the following aspects.(1) A new type of composite joint, composite enforced loop joint, connecting is proposed. Through the experimental study of eight joints of the concrete filled steel tube column and the composite beam, the initial stiffness of the joints are analyzed in detail considering the influence of the line stiffness ratio of beam and column, compression ratio of column and slenderness ratio axial, and the rule of the load and strain on the joints are studied.(2) The theoretical formula of the initial tensile and compressive stiffness of the composite enforced loop of the composite frame structure side joint is proposed according to elastic mechanics, and the major factors that affect its stiffness are analyzed. And finite element method is used to verify the theoretical formula result of the composite enforced loop of the composite frame structure side joint.(3) The methods of calculating the initial tensile stiffness of the enforced loop of the concrete-filled steel tube column-steel beam interior joint and the composite enforced loop of the concrete-filled steel tube column-composite beam joint are proposed according to energy method. And the contribution of the concrete slab in the composite enforce loop, which is used to improve the initial tensile stiffness of the composite frame interior joint, is analyzed. (4) The transfer mechanism and failure mode of the composite enforced loop joint are investigated. The method of calculating its shear resistance is studied. The shear resistance of eight composite enforced loop joints in the test are calculated and studied.