| The structure of the Concentrically Braced Frames(CBFs)is simple and the lateral stiffness is large,but it is difficult to avoid the buckling and instability of the brace in the seismic load,which causes the stiffness of the structure to drop sharply and the story displacement to exceed the limit value,causing great damage to the structure.On this basis,the buckling restrained brace(BRB)is introduced to replace the common brace to solve the instability problem of th e brace and form the Special Central Bracing Frame(SCBF).The buckling-restrained brace can act as a common brace under the action of small earthquakes to pr ovide lateral rigidity for the steel frame.As the first line of defense of the structure,due to the existence of external restraint mechanisms,the buckling-restrained brace yield without buckling and dissipates seismic energy under the action of large earthquakes.However,in the traditional structural design,the buckling-restrained brace and the frame are connected by welded joint plates,it was found that the weld seam at the joint plate is brittle broken on account of stretching opening and closing effect,which forces the buckling-restrained brace to withdraw from work ahead of time,affecting t he safety and reliability of the structure under seismic action.In view of the problems mentioned above,a connector is introduced into the design of the buckling-restrained brace,the frame structure can be divided into parts,and then the structure can be assembled and formed by bolts to form prefabricated concrete structure,giving full play to the advantages of prefabricated concrete structure;besides,the introduction of the connector can replace the connection of traditional joint plates to relieve the stress in the joint region.Through the reasonable design of the connector,the connector,as an energy dissipation,firstly yields to dissipate earthquake energy and plastic deformation is concentrated on the connector,thus protecting the safety of the main structure under the action of earthquake.Based on the finite element analysis and experimental research,the influence of the introduction of the connector on the bearing capacity,energy dissipation performance,stress distribution,rigidity and ductility of the steel frame is study,the influence of connectors with different parameters on th e performance of steel frames is analyzed in this paper,and the seismic performance of the improved specimen is analyzed.the following conclusions can be listed.(1)According to the analysis of the finite-element and experiment research,it is found that the introduction of connectors can obviously relieve t he stress in the joint region of joint.the stress in the joint region remains elastic and does not r each yield under the elastic-plastic inter-layer displacement.(2)During the loading process,the connector firstly yields and dissipates energy,accumulates plastic deformation in the energy dissipation section,and then the buckling-restrained brace begins to yield and acts as a supplementary energy dissipation element.The finite element and experimental research show that the specimen has a full hysteretic curve and good energy dissipation performance.(3)The axial overstrength factor of n≤1 has little effect on the bearing capacity of the structure,when the axial overstrength factor n>1,the bearing capacity increases rapidly,but the bearing capacity begins to decrease as it continues to grow.In this paper,it is suggested that the axial overstrength factor should be1.05～1.30.The width-to-thickness ratio of the connecting plate has an important effect on the performance of the structure.In this paper,it is suggested to take7～10.However,the energy dissipation length of the connector has little effect on the performance of the structure due to the existence of the external constraint bushing.(4)After improving the drawbacks of the buckling-restrained brace during the test,it was found that the brace can stably bear force and ensure reliable force transmission. |
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