Seismic Behavior Of Steel Moment Connections Using Replaceable Buckling-restrained Energy Dissipation Fuses

Steel beam-column connections have always been a key part of steel moment frames,transferring bending moment and shear force,while dissipating the earthquake energy.But the previous earthquake shows that the welded beam-to-column connection of steel frame are prone to brittle fracture.The bearing capacity of the connection decreases considerably after yielding and the range of the plastic zone of the connection can not be effectively controlled,which makes it difficult to repair the structure after earthquake.So we make use buckling restraint and damage control to propose a new type of recoverable steel beam-to-column connections using buckling-restrained energy dissipation fuses.Analyse mechanical properties and the feasibility of post-earthquake repair by low cycle reciprocating load test and finite element analysis.Finally,we propose a equivalent mechanical model of connection and design method.(1)Definite the configuration of the new connection and propose the equivalent mechanical model by load transfer and deformation mechanism.And approach the calculation method of equal stiffness and bearing capacity,including ultimate bearing capacity and ultimate rotation,yield bearing capacity and yield rotation.(2)Propose the design method of new connection using the equivalent mechanical model,including equal stiffness and damage control design method.Obtain the design process:strong column and weak beam—strong beam and weak buckling-restrained energy dissipation fuses—strong connect and weak energy dissipation fuses.(3)Design one group of retrieval steel beam-to-column connections test and three group of replaceable components to make low-cyclic loading test.Provide load transfer and deformation mechanism and the feasibility of post-earthquake repair by observing the change of displacement-bearing capacity,plastic development in the end of the beam,the drum deformation of energy dissipation fuses.(4)Deeply analyse the hysteresis loop,the skeleton curve,dissipation capability,equivalent viscous damping ratio,effective stiffness and the status of stress and strain in the flange.Discuss the specific impacts and reasons of two construction technology of bolt preload and weakening method in energy dissipation fuses.Verificate the feasibility of equal stiffness and damage control design method.(5)Choose the fracture location of connection,the flange expansion method of cantilever beam,the buckling-restrained cover plate,the stiffening rib of c-shaped shear plate,weakening method of energy dissipation fuses and the span-depth ratio to build ten finite element models.Deeply analyse the stress-strain,displacement bearing capacity and initial rotational stiffness.Verificate the validity of the initial rotational stiffness calculating method.Provide the calculating method of the limits of span-thickness ratio.Provide the opinions about the uses in engineering practice.