Research On Collapse Analysis Of BRB RC Frame Structure Under Rare And Extremely Rare Earthquake

Normal brace which is under compression will easily buckle.When the brace is buckled,the stiffness and bearing capacity are drastically reduced.When the brace is gradually changed from the buckled state to the tensioned state,the inner force and stiffness are close to zero.So the hysteresis performance of normal braces under repeated load is poor.BRB(Buckling restrained brace)is a new kind of energy-consumpting brace.The biggest difference between BRB and traditional brace is that the main energy-consumpting part of BRB,kernel unit,is restrained by constraint unit,so that BRB under compression will not buckle before full section yielding.In this way,BRB can avoid the instability problem that traditional brace usually faces.BRB has good ductility and hysteresis performance.In the elastic stage,BRB can provide a great deal of lateral stiffness to resist small earthquakes and wind loads.In plastic stage,BRB has great deformation ability and hysteretic behavior to help the sructure resist strong earthquakes and improve the collapse resistance of structures.The frame structure with BRB(hereinafter referred to as BRB frame)can reduce the design reinforcement,So it is a problem that deserves researchers' attention whether the seismic fortification requirements can meet the requirement of No Collapsing in the Strong Earthquake.This paper uses the numerical simulation method to analyze the seismic behavior of frames and BRB frames of different size,different height,different space arrangement,including a three-layer frame and a five-layer frame based on seismic fortification of 6 degree,7 degree,8 degree,9 degree and other four frames,under the rare earthquake and extremely rare earthquake.Seismic behavior is embodied in the structure of the inter story deformation,base shear,the number and development of plastic hinge and vertical component energy consumption,etc..By comparing the FEM analysis of BRB frames and frames,conclusions are as follows:(1)Thanking to excellent energy dissipation capacity of BRB,seismic responses of BRB frames are weakened and BRB frames can meet the requirement of No Collapsing in the Strong Earthquake.(2)The drift of the frame and BRB frame under the rare earthquake can meet the specification requirements.Under the extremely rare earthquake,the maximum drift(3)of the frame in the region of intensity 6 is less than 1/50.The maximum drift of the frame in the region of intensity 7 is very close to 1/50.In the region of intensity 8 and 9,this value is larger than 1/50.The drift of BRB frames of different intensity areas can meet the specification requirements.BRB frames have a high security reserve,which can prevent the collapse of the structure under the superstrong earthquake.In the early 90 s,American scholars proposed the performance-based seismic design theory.Under the guidance of this idea,many scholars put forward their displacement-based seismic design method.On the basis of their research,this paper deduces the theoretical formula of the stirrup characteristic value from the related basic assumptions and some theoretical results.The mean value of the maximum inter story drift of different BRB frames which is obtained by the FEM analysis is put into the formula.Thus,the suggested value of the stirrup characteristic value of BRB frames is obtained.