The Finite Element Analysis Of The Typical Ductile Connection With Reduced Beam Section And Widened Beam Flanges In Steel Frame

The rigid joints of steel frame appeared lots of brittle failure and the beams didn't appear plastic deformation obviously or plastic deformation didn't happen at all under the earthquake load. According to these problems, in order to improve joint properties to avoid brittle rupture, this paper performs the finite element analysis on the new ductile node from the view of ductility through ANSYS. There are two kinds of the new ductile node: reduced beam section(also called dog-bone section) and connection with widened beam flanges. The result showed that these two connections are feasible theoretically and practically. The position of plastic hinge in dog-bone section joint moves to the weakened department of beam flanges. And the position of plastic hinge in connection with widened beam flanges moves to the end of the arc segment of widened flanges. Both are far away from the weakness of beam-to-column connection, which is easy to appear brittle fracture. And in the beam-to-column connection, both stresses and degree of stress concentration decrease. According to the strong column weak beam principles of anti-seismic design of steel frames, it matches the idea of making plastic hinges of beams away from connection area and apply to make the plastic hinge away from the connection. The ultimate bearing capacity of dog-bone section joint reduces because of weakened beam flanges. But the ultimate bearing capacity of widened beam flanges joint is greater than the traditional rigid connection. As a result, it is suggested that connections with widened beam flanges are selected firstly in the design of beam-to-column connection in steel frames to meet anti-seismic requirements.Elastic and el-plastic finite element analysis is made on the joints on which weakening parameters of reduced beam section joint and designing parameters of connection with widened beam flanges change, and the effect of the changes of these weakening and designing parameters on joint properties has been analyzed from the aspect of stress and load-carrying of joints. It will satisfy the purpose of plastic hinge moving outside to select the bigger parameters of dog-bone section joint. But the value should not be too large, otherwise the load capacity of the joint will be damaged. Also the appreciate increase of the widened beam flanges dimension is useful to enhance the seismic behavior and the load capacity. Finally, the scale of the parameters is suggested based on the research result.The scale of the parameters of this two typical ductile connection is suggested from the above research result. It is determined that the length, depth and distance to column flange of dog-bone section joint and the length, width of widened flanges and arc segment of connection with widened beam flanges. These seismic behavior satisfies the ductility and provides a basis for engineering design.