Seismic And Shock Absorption Analysis Of High-rise Plane Irregular Steel Frame Bracing System

Planar irregular steel frame structures have been established in many cities,and many cities are on seismic zones in China.This makes the plane irregular steel frame structure extremely vulnerable to earthquake threat.Under earthquake action,plane irregular steel frame structure is more complicated than regular steel frame structure,and it is easy to produce weak stories which lead to structural damage.Many experts and scholars at home and abroad have done a lot of experiments on the seismic response of plane irregular steel frame structures,and combined with the corresponding simulation data,the research results are of great significance.In order to further enrich the research results of seismic and shock absorption performance of irregular steel frame structures.In this paper,the seismic performance of a plane irregular steel frame structure under different braces and the seismic performance of viscous dampers under rare earthquakes are studied.The main contents and conclusions of this paper are as follows:(1)In this paper,firstly,the hazards of earthquakes and the development status of steel structures are summarized.At the same time,the research and development status of irregular structures and different supporting systems are introduced.Then the seismic theories of modal analysis,response spectrum analysis and time history analysis are introduced.(2)Based on the research and development status of irregular structure and steel frame bracing system,and combined with relevant engineering practice,four kinds of plane irregular steel frame models are established by SAP2000 finite element analysis software: model 1(pure steel frame structure),model 2(with X-shaped bracing),model 3(with herringbone bracing)and model 4(with octagonal bracing).The modal analysis of the four models is carried out,and the natural vibration period and the translation and torsion properties of the structure are obtained.After analysis,it is concluded that the bracing can improve the stiffness of the structure(X and Y directions),reduce the natural vibration period of the structure,and prevent the early appearance of torsional modes.At the same time,it can be seen that for the first three cycles,the reduction period of adding X-brace and H-brace is more obvious than adding H-brace.It also shows that adding X-brace and H-brace is more obvious than adding H-brace in improving structural stiffness.(3)The response spectrum analysis of the four models shows that the effect of X-brace(center brace)on reducing the maximum displacement and the maximuminter-story displacement angle is similar to that of herringbone brace(center brace),and the effect of octagonal brace(eccentric brace)is the worst.(4)Linear time-history analysis of four models(under frequent earthquakes)is carried out.Through the analysis of floor displacement,inter-story displacement angle,inter-story shear force,top-story displacement,top-story acceleration,base shear force and base bending moment,it is concluded that under linear time-history analysis,the lateral stiffness of central support(X-shaped support,herringbone support)is higher than that of eccentric support(octagonal support).Support)works better.At the same time,the effect of X-shaped support is slightly better than that of herringbone support.(5)Nonlinear time history analysis of four models(under rare earthquakes)shows that eccentric bracing(octagonal bracing)reduces floor displacement more significantly than central bracing(X bracing and herringbone bracing)in the X-direction of the structure,which shows that eccentrically braced energy-dissipating beam section consumes more energy under rare earthquakes.For the Y direction of the structure,the conclusion is opposite.In the non-linear time history analysis,the floor where the maximum inter-story displacement angle is located can be considered as a weak layer,and corresponding seismic and reinforcement measures can be taken.(6)In order to ensure the safety of structures under rare earthquakes,a kind of viscous damper is selected for energy dissipation and seismic reduction analysis.Model 5(obtained by adding viscous dampers to model 1)and Model 6(obtained by adding viscous dampers to model 2)were established by SAP2000 software.Nonlinear time-history analysis of the two models shows that: floor displacement,inter-story displacement angle,inter-story shear force,top-story displacement,top-story acceleration and hysteretic curve,and compares model 5 and Model 6 with model 1 and model 2 of the previous non-linear time-history analysis respectively.It is concluded that viscous dampers can consume part of seismic force,reduce floor displacement and the maximum inter-story displacement angle curve under rare earthquakes.And viscous dampers improves the seismic capacity of the structure.At the same time,the plumpness of hysteretic curve is analyzed,and the viscous damper has better energy dissipation ability.