Seismic Performance Analysis Of Steel Framebuckling Restrained Brace Structure

Because of the advantages of lightweight and high strength,rapid construction and flexible arrangement of space,the steel structure has been widely used in the engineering construction.However,the pure steel frame structure with good ductility and relatively smaller cross section usually can’t meet the requirements in lateral stiffness and deformation.Frame-braces system is commonly used to supplement the inadequate of lateral capacity of pure frame structure.Ordinary steel braces are prone to occur compressive buckling and quit work under severe earthquake,which resulted in the seismic capacity of the whole structure declining sharply until destroyed.In order to improve the performance of braces,Japan developed a new type of brace-buckling restrained brace(BRB).BRB can provide lateral stiffness for the structure at elastic stage,while at the plastic stage,it can achieve full section yield without buckling.In addition,as a component of energy dissipation,its core board is made up with low yield point steel.When the severe earthquake comes,BRB plays as the first defence line of the structure.It enters the plastic stage to dissipate the seismic energy firstly,so as to protect the main structure.The study and application of BRB in China is still in its infancy.The importance of BRB in engineering has not been explicitly refected.Based on the actual project-Shijiazhuang Swimming Gym,this paper presents the advantages of BRB compared to ordinary braces by modeling and analysis,specifically as follows:1)The theory of BRB is introduced,including its working principle,the method of calculating various parameters and mechanical conditions to guarantee that it will achieve yield state without buckling;2)The structure of steel frame-buckling restrained brace is introduced and the effect of BRB on structural damping and vibration period is given;3)According to the project,this paper models two structures of pure frame structure and steel braced frame structure by the SAP2000.The analysis results of vibration period、drift、shear force and shear-weight ratio under elastic response spectrum load case are compared.Results show that the lateral stiffness of second model increases,and the displacement and shear-weight ratio getting to meet the requirements of the standards after adding the braces;4)Firstly,according to the elastic analysis model,structures are further subdivided intothree models: the pure frame model、ordinary steel braced frame model and the steel frame with BRB model.Secondly,elastic and plastic time history analysis are made on the three structures by using Perform-3D software.Thirdly,the base shear of three structures under the elastic time history are compared with the results under elastic response spectrum.Fourthly,the drift、displacement of the top point、damage of components and energy consumption of the three models under plastic time history load case are compared.Finally,a comparison of hysteresis loops between the ordinary brace and the BRB are made.Results show that:ordinary braces and BRB both can improve the seismic performance of frame structures.But the hysteresis loops of BRB are fuller and it can dissipate more seismic energy.Structures with reasonable arrangement of BRB can be protected better and achieve a higher degree of fortification.