The Seismic Performance Study On Beam-to-Column Modified Rigid Connection Of Steel Frame

During the 1994 Northridge earthquake and the 1995 Kobe earthquake, great amounts of beam-to-column connections brittle fractures were found in steel moment frame. Relocating the plastic hinge is the main modified idea for connection in steel moment frame. These modifications are strengthening and weakening methods. Both strategies effectively move the plastic hinge away from the face of the column, So that the end weld could be protected and the ductility as well as the energy dissipation capacity of the connection could be improved. But two types of connections have advantage and disadvantage, In this thesis, Strengthen-Weakened Connections were presented in beam-to-column rigid connection, experimental and theoretical research were conducted to investigate the seismic behavior of two of Strengthen-Weakened Connections and a Strengthen ConnectionsIn this thesis, a full-scale Widen Flange-DogBone Connection(Welded-Bolted connection), a full-scale Widen Flange-DogBone Connection(Welded connection)and a full-scale Plate Strengthen-Dog Bone Connection suggested in the standard atlas of"connection details in multi-storey and high-rise steel structures"(01SG519) were tested under cycle loading; a full-scale Trapezoid-Widen Flange Connection in steel moment frame was tested; Further more, Beam Strengthening-Bolt Spliced Connection were firstly tested to investigate their ultimate bearing capacity, the development of plastic hinge, plastic rotation, energy dissipation and ductility.On the other hand, finite element analyses on experimental specimens have been executed by using ABAQUS. The geometric nonlinearity, material nonlinearity and contact nonlinearity, bauschinger effect, weld defects, pre-tension of high strength bolts were all taken into account in analyses. The analyses results were compared with experimental data. Then a series of parametric finite element analyses about three different kinds of connection and advantages of the Strengthen-Weakened Connection were executed for remedying experimental shortage. According the FEA results, the influence of each factor on seismic performance was discussed and the design proposals were made. The load -displacement hysteresis curve and the development of plastic hinge from FEA result fit in the experiment, which could confirm the feasibility and creditability of choice of unit type, material property and the hardening rules. The FEA method would provide a reference for similar theoretical analyses. The results of tests and FEA showed that, the plastic rotation and energy dissipation capacity of the Strengthen-Weakened Connection and Trapezoid -Widen Flange Connection all exhibited excellent. Beam Strengthen- Bolt Spliced Connection can effectively make the relocation of the plastic hinge and brittle fractures of the end welding could be avoid effectively due to end welding of beam was made in factory and splice connection were all with high-strength bolts. Especially, Beam Strengthen-Bolt Spliced Connection with single gusset have economic advantage and convenient for construction. Above-mentioned beam-to-column connections were recommended for applying in the steel moment frames.