Study On Earthquake-resistant Behavior Of Enforced Loop Of CFST

With the development of the theory of the concrete filled steel-tubular structure and the comprehensive using in engineering, the node of the concrete filled steel-tubular column and steel beam connections is becoming one of the most important technique problems of researching and generalizing in the concrete filled steel-tubular structure. So it is becoming a most important assignment with the extremely important practical significance regarding the instruction design work that study the various parameters'influence to the seismic-resistant performance of node and even better coordinating the relationship between the structure's strength, rigidity and ductility.Using the general finite element programming package of ANSYS10.0, this paper systematically analyzes the overall behaviors of the bolt and welt connections, synthetically considering nonlinear (material, geometry and contact) factors. In this paper, it simulates and analyzes the stress of 5 series sample considering the form of enforced loop plane, the breadth of enforced loop plane, the thickness of enforced loop plane, the ratio of pulldown and the effection of gradation of concrete and steel. Through the study of finite element, it makes some chief conclusions as follows: In the different frame of enforced loop joint of the concrete filled steel-tubular column and steel beam, the endogen force of BASE.HUFM3 joints have uniform distribution, the connection of enforced loop joint and steel beam has minor plastic region, and the web of steel beam has minor stress. HUFM1.HUFM2 joints have higher bearing capacity, but thy have heavier stress concentration than BASE.HUFM3 joints. And there are higher at the connection of enforced loop joint and steel beam and the web of steel beam. BASE.HUFM3 joints will be recommended; Width of enforced loop joint in(0.7~1.2)B will be the most effective; With thickness of increased enforced loop joint the bearing capacity of joint has been improved obviously. So the thickness of enforced loop plane is important factors that affect bearing capacity of joint; The results show that the ratio of pulldown in (n≤0.8Ny)has little affect on joint bearing capacity elastic stiffness and tensility; The concrete gradation has little affect on joint bearing capacity elastic stiffness, but the steel pipe with concrete has more affect on improving steel pipe bearing capacity; The steel intensity has more affect on the joint bearing capacity stiffness, but relative intensity and deforming capability reduce.The study analyzes the concrete filled steel-tubular column and steel beam connections'load-bearing performance in a rather comprehensive and systematic way, and the conclusions can be useful for amending design code, guiding design of engineering, and provide good basis for further study of seismic-resistant behavior of other types of nodes.