Experimental Research And Finite Element Analysis Of Buckling Restrained Brace With Ductile Casting Connectors

The special center support steel frame system is a kind of structural system which is widely used in seismic areas.It combines the advantages of high bearing performance of the special bending frame.The brace is the key component that affects the performance of the structure and determines the seismic performance of SCBFs,such as strength,stiffness,energy dissipation and ductility.And the yield mechanism,the inelastic deformation ability and the final failure mode are closely related to the connection way of the brace.However,in the existing structural design,the brace is buckled and connected with the beam and column through the joint plate,which makes the distribution of the region stress complex and easily produces high triaxial stress field and brittle fracture.Meanwhile,the brace will prematurely buckling or breaking,and its energy performance can not give full play.In order to ensure that the brace does not occur buckling instability,low-cycle fatigue damage and brittle fracture while inelastic deformation energy consumption occurs,so as to meet the expected level of seismic performance of the structure,the brace structure of the special center support steel frame is proposed and designed as a brace system with ductile casting connectors that is,the ductile casting standard connector is set at both ends of the brace to make the brace,beam and column connect together.Through reasonable geometric design,the inelastic deformation ability of the brace can be controlled,the stress distribution of beam and column can get relieved and the non-ductile damage can be eliminated.Secondly,the buckling restrained brace is introduced instead of the brace of the special center support frame,and the buckling behavior of the buckling restrained brace is used to ensure the smoothness of the structural transmission path,so as to give full play to the non-elastic deformation energy consumption.In order to study the performance of steel frame with buckling restrained brace with ductile casting connectors,the study of the buckling restrained brace with ductile casting was carried out at first.Combining experimental study with finite element analysis,the buckling restrained brace with ductile casting connectors of different parameters are analyzed,the conclusions are as follows:(1)Under monotonic loading,casting energy dissipation segment connections first enters the yield stage;ultimate failure,the energy dissipation segment total cross section in the plastic yield stage,BRB core tube multi order buckling phenomenon,connection section and transition section most is still in elastic stage,which does not cause the stress concentration of beam column joints,protection the role of node.(2)The ductility ratio of specimens is affected by the factors such as the length of energy dissipation section,the ratio of stiffener to width and the ratio of width to thickness of energy dissipation plate.Among them,the impact ratio of energy dissipation plate is most significant.With the increasing of the width ratio of the energy dissipation plate,the ductility ratio of specimen decreases.(3)Under the cyclic load,the hysteretic behavior of the specimen is stable and the energy dissipation is good.The buckling restrained brace with ductile casting connectors is in a state of elasticity before the specimen reaches the ultimate load,and the casting joint yields and dissipates most of the energy.After reaching the ultimate load,the buckling restrained brace begins to yield energy,and the energy dissipated with the ductile casting joint,the BRB plays a role in supplementing energy consumption and the energy dissipated with the ductile casting joint.But a smaller degree of stiffness degradation occurs during the cyclic loading.(4)It is found that the deformation of the buckling restrained brace with ductile casting connectors are concentrated in the energy dissipation section during destruction,and the deformation of the casting parts is greater than that of the buckling restrained brace,which achieves the goal of concentrating the deformation in casting joints.