Performance Analysis And Improvement Of Flange Reinforced Dog-bone Connection

After the Northridge and Kobe earthquakes, extensive experimental and numerical studies on the mechanical performance of beam-column connections were conducted by many scholars. The plastic deformation capacity of connection is improved mainly though strengthening connection or weakening member. Based on deepening of the concept, that is to say strong connection and weak member, an improved beam-column connection is designed by locally widening flange at the end of beam, and weakening flange at a certain distance away from the beam end (which called flange reinforced dog-bone connection hereunder).This improved connection can make the plastic hinge far from the beam-column connection with stronger bearing capacity and better ductility.In this thesis, a nonlinear finite element analysis about the widen flange connection based on an experiment is firstly conducted by ANSYS, and the results are compared with the experimental results. The hysteretic curves demonstrate that the finite element analysis can factually reflect plastic deformation and bearing capacity of the connection.Based on the above experimental model, we scheme out the three forms of beam-column connections, namely, flange reinforced dog-bone connection, dog-bone connection and ordinary moment connection. Because of the above finite element analysis results about the widen flange connection has been already validated, it is reliable and effective that the three types analyses of beam-column connections under cyclic load are also conducted with the same analysis method. The results demonstrate that the energy dissipative and ductile capacity of the flange reinforced dog-bone connection is strengthened effectively because of the plastic hinge formed far from the beam-column connection; as well as its bearing capacity and initial stiffness are significantly higher than dog-bone connection; for comparing with widen flange connection, although the flanges at the beam end of flange reinforced dog-bone connection are widened, but the reinforced amplitude is smaller than widen flange connection, so it is needless to increase the column section; thus bring out the purpose of saving steel. In order to define the stress distribution and development rules of beam flange, beam web and connection region, the four kinds of connection models are established by ANSYS. The vertical downward compulsory displacement is applied at the beam-end, and the 3-D nonlinear finite element analysis under monotonic load is accomplished. Then, the stress distributions of model at the elastic and elastic-plastic stages are obtained. The results show that the flange reinforced dog-bone connection is very well which plastic hinge is shift away from the beam-column connection, not only without increasing column section, but also the welding quality at the end of beam is more easily guaranteed.Three series of flange reinforced dog-bone connections are designed for making the length and depth of weakened part, the length of widened flange more reasonable. By using the finite element programs with considering material nonlinear and geometric nonlinear, the influence on the behavior of flange reinforced dog-bone connection with widen beam flange length, weakened beam flange length and depth are discussed respectively. Puts forward some suggestions on the range of design parameters of flange reinforced dog-bone connection, and provides a basis for engineering design.