| The earthquake resilient structure is the research hotspot of earthquake engineering,and the structure with replaceable energy dissipation components is one of the important constructions to realize the seismic resilience.A large number of brittle failure occurred in beam-column joints of traditional welded steel frames in the Northridge earthquake and the Hanshin earthquake.At present,many scholars have studied the plastic hinge transfer type joints such as weakened and strengthened joints.The plastic hinge is transferred to the area far from the joint connection to improve the seismic performance of the joints.However,they overall do not offer the post-earthquake repair strategy,and the seismic resilience needs to be improved.Therefore,some scholars set various forms of replaceable energy dissipation components in the steel frame beam-column joints to achieve rapid assembly and convenient post-earthquake repair.Buckling-restrained energy dissipation components have a dual function of bearing and energy dissipation with high ductility,which can effectively build seismic resilient beam-column joints.In this paper,the concept of buckling restraint is introduced into the joint,and a steel frame beam-column joint with replaceable U-shaped buckling restrained connector(RUBRC joint)is proposed.The seismic performance and design method of RUBRC joint are investigated through quasi-static test,numerical simulation and theoretical analysis.The main research work is as follows:RUBRC joints with five connection forms under cyclic loading were conducted and compared in the failure mode,hysteresis curves,skeleton curves and energy dissipation capacity,and the effects of the stiffeners,web connection form and buckling restrained system on the hysteretic performance of the joint are discussed.The test results show that the joints with hinged or bolted web connections have good hysteresis performance;the constraint effect of the cover plate on the core plate is obvious,which ensures the stability of the bearing capacity and stiffness of the joint after yielding.The joint proposed in this paper can limit the damage to the RUBRC,and the main part of the beam and column remains elastic.The finite element software ABAQUS is adopted to simulate the proposed RUBRC joint.The comparison test results show that the finite element model can well simulate the hysteretic response of RUBRC joint under cyclic loading.On this basis,the parameters of the joint are analyzed,and the effects of the friction force of the core and web bolt spacing on the seismic performance of joints are discussed.The parameter analysis results of the joint model show that the fuller hysteresis curve can be obtained through increasing the friction force between the core plate and restrained plate;The change of friction force of the web connection plate has little effect on the initial stiffness and sliding load of the joint,but has great influence on the yield load and bearing capacity of the joint.The theoretical analysis of the RUBRC joint is carried out,and the calculation formulas of the strength and initial stiffness of the joint are derived.At the same time,the design process and method of joint are given,mainly including the design of core plate,buckling restrained system,end plate and ear plate.36 parametric numerical models are constructed in this paper,and the derived formulae and design theories are verified.The results show that the joints designed by the proposed method can meet the expected design goals.The area of the core plate affects the initial stiffness,yield and ultimate strength of the joint;the size of the bolt and the thickness of the end plate should be reasonably selected to achieve reliable connection;the buckling-restrained system has an important influence on the performance of the joint. |
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