Research On Seismic Behavior And Design Method Of A New Type Of Buckling-restrained Braced Steel Frame

The buckling-restrained brace(BRB)has a stable load carrying capacity and is widely used in the frame structure.The stiffness of the frame can be increased by introducing BRBs,at the same time,the seismic energy can be dissipated and the seismic response of the structure can be reduced.In China,the application of buckling-restraint brace is still in the initial stage,there are a series of problems such as manufacturing difficulty,high cost and imperfect design method,which greatly limits the promotion and application of the BRB.Based on a large number of research results at domestic and abroad,this paper designs a new type of BRB and improves the displacement-based seismic design method,which is suitable for the design of buckling-restrained braced frames(BRBF).In this paper,a new type of BRB designed,by applying prestress in the core unit,so that it has the characteristics of premature yield,before the peak of the earthquake began to dissipate energy,reducing the accumulation of energy in the structure,play a role in structure protection.The load carrying capacity of the new brace is analyzed by means of theoretical deduced method,and the bending-torsional buckling of the bucklingrestrained machine is studied emphatically,and the formula of the stability of the external constraint is proposed.The main parameters affecting the mechanical properties of the new brace are analyzed by numerical simulation,and the conclusion is drawn that it is sensitive to the ratio of gap to thickness.It is suggested that the ratio should not exceed 10% theoretically.Considering the strong nonlinearity of the BRBF,the nonlinear system is equivalent to the linear system according to the principle of "equal displacement response",and the calculation of equivalent lateral stiffness and equivalent damping ratio is given;There are new methods in displacement-based seismic design(DBSD): the fundamental mode of the structure is used as the shape vector of the target displacement,the fundamental period of the MDOF system is used as the equivalent natural period of the SDOF system.A new type of BRBF is designed by using the improved DBSD method,and the mechanical performance of the frame is analyzed by ABAQUS software.When the static elasto-plastic analysis is carried out,the development order of the plasticity is BRBs—beams of the frame—columns of the frame,which achieves the purpose of multi-channel fortification.In the case of time-history analysis under rare earthquakes,the interstorey drifts of the new type of BRBF is generally less than the ordinary BRBF's,and both are less than the limit of interstorey drifts.Setting up the new BRB can reduce the structure seismic response,the structure designed with improved DBSD can meet the seismic requirements.