Study On Seismic Performance Of Fully-fabricated Beam-to-column Joint

Various earthquake shows that the construction based on the existing seismic design method which limits the bearing capacity and elastoplastic story drift ratio can reach the three-level seismic fortification target,ensuring the safety of human life.However,this method is difficult to effectively control the damage of structure,leading to the results of serious economic loss due to loss of service ability and construction repairing.Aiming at more and more financial loss in recent years caused by earthquake,some shcolars proposed that the seismic design method that simply set the life safety and reduce the direct economic loss as the goal should be taken place,and people should focus more on resilience ability of modern structure under extreme disasters.Normal service ability is supposed to be recovered within short time,which implicates the seismic design concept transformation from shock absorption to resilience structure design.Under this background,seismic joints and novel structure of resilience ability is in rapid development.A new type of friction energy-dissipated beam-to-column joint with post-earthquake recovery of service function is proposed.Beam-to-column connection is composed of composite joint and friction damper.Composite joint includes UHPC?steel flange?steel end plate and stiffener,and the composite joint is connected with beam and column with bolts.While friction damper includes three parts of steel plates and it is pined to beam and column through ear plates.Under normal service or frequent earthquake,friction damper is equivalent to a rigid rod without sliding,providing relatively large initial stiffness for the structure.Under the effect of rare earthquake,when the friction force caused by the bending moment at the joint is greater than the maximum static friction force,the friction plate will slide and the structure will experience large rotational deformation at designed plastic hinge area.The sliding deformation of the friction damper consumes more than 60% of the input energy,meanwhile the main body of the structure beam and column will only experience elastic deformation without plastic deformation.The function of restoring normal use of the structure after earthquake can be achieved by adjusting the pre-tightening force of the high-strength bolt or partially replacing the connector.The experiment of four connector specimen is conducted to study the seismic performance of the joint based on cracking pattern,yielding load,stiffness,stain distribution,hysteresis curve as well as ability of energy dissipation and so on etc.Besides,the analytical model of yielding load and initial stiffness is deduced.The hysteresis curve simulated by ABAQUS can fit well with the experiment data,proving the efficiency of simulated model.Besides,the analytical model of yielding load and initial stiffness is deduced.The hysteresis curve simulated by ABAQUS is obtained,which can fit well with the experiment data,proving the efficiency of simulated model.Besides,pushover analysis and nonlinear dynamic analyses of conventional steel frame and novel frames were carried out by using ABAQUS.The results showed that both deformation and base shear force of the novel frames were significantly reduced in the simulations compared with conventional frame.Under maximum considered earthquake(MCE),the conventional steel frame sustained significant yielding in the beam-column connection and column base.While for the novel frames,more than 80% external works were dissipated by the friction dampers,and only slight plastic strain appeared on the composite UHPC joint and column base,demonstrating the realization of the expected damage tolerant performance.Furthermore,it is found by comparison that the early yielding mechanism caused by the weak friction dampers can effectively improve the energy dissipation performance and damage control.