Study On The Effect Of Mixed Arrangement Of Buckling Restraint Braces On Seismic Performance Of Frame Structures

With the improvement of seismic fortification requirements,it is not economical to simply increase the material strength,reinforcement ratio or increase the cross-sectional area of components to meet the seismic requirements of high-intensity areas.At present,the bracing frame structure is a multiple lateral force resistance system.The brace is the first seismic line of defense.When it fails,the frame acts as the second seismic line of defense,which will bear all lateral loads and provide a safety reserve for the structure.Buckling-Restrained Braces(BRB),as a typical shock-absorbing and energy-consuming braced element,solves the defect that ordinary braces are prone to out-of-plane buckling and instability under compression,can achieve full-section yield under tension or compression,and can achieve strong characteristics such as tension and compression.In Buckling-Restrained Braced Frame(BRBF),BRB is the first to yield and not buckle during a major earthquake,using full hysteresis curve to consume seismic energy and achieve the purpose of damping.The research on BRB and BRBF in my country started relatively late.Due to different types of BRB have their own patent rights,the cost of BRB is relatively high(patent fees).If BRB is used as bracing members in all ordinary buildings,it will lead to the problem of low economy.In order to improve the seismic performance of buildings,and promote the promotion of BRB in a large area in my country,this paper studies the rational layout of BRB in frame structures.The lateral stiffness ratio k between the brace and the frame is one of the important steps in the design of BRBF based on displacement.In view of the problem that the existing BRB section determined by the "fixed k value method" will cause excessive performance of the BRB on the upper part of the structure,the influence of Buckling-Restrained Braced Frame structure based on "fixed k value method" and "reduced k value method" is studied through finite element numerical simulation,from the perspective of deformation and energy,in the third chapter.The calculation results show that the BRBF based on the "reduced k value method" can reduce the steel usage of the inner core unit about 12.5% to 37.5% without changing the position and size of the maximum interlayer displacement angle of the structure.On the basis of the above conclusions,the recommended value of lateral stiffness ratio k is given.In order to reduce the usage amount of BRB on the premise of ensuring the structural performance,a scheme of replacing part of BRB with ordinary bracing is proposed in this paper.By comparing the pushover analysis of BRBF,Concentrically Braced Frame(CBF)and the mixed braces frame structure with different "replacement rate" schemes,the rationality of the mixed braces frame structure scheme is verified.On this basis,considering economy and earthquake resistance comprehensively,the suggested interval and matters needing attention for the "replacement rate" of the hybrid braces are given.