Research On Seismic Design Method Of Steel BRB-frame Structure

High-rise steel frame system has good ductility, nevertheless, the displacement ofthe structure is too large under the action of lateral load because of its small resist lateralstiffness, this problem are waiting to be tackle, so it is very important to choose anddesign lateral resisting system. The conventional frame-bracing systems have greatlateral stiffness in elastic, however, the ability of its displacement is small and thebraces will be easily buckled when it is undergoing compression, and then the framewill be destroyed by the lateral load. Buckling-restrained brace can overcome thedisadvantage of conventional brace which easily buckles under compression. Rationaldesign buckling-restrained brace can not only enhance the stiffness of frame, but also toensure it yields in beginning at severe earthquake and the main structure is protected, sohelp to improve the seismic performance of the structure.However, how to use buckling-restrained brace just in a preliminary stage, andhow to design reasonably is a practical problem deserved research, so it is necessary toresearch for a design method which is actual and feasible for buckling-restrained brace.Firstly, basing on a large number of research results and design theory at home andabroad, this thesis proposes a simple and workable design method aboutbuckling-restrained brace frame by analysis and calculation.Secondly, using the method proposed in this dissertation to designbuckling-restrained brace steel frame, and using the software Midas to carry on thetime-history analysis for the buckling-restrained brace steel frame and conventionalbrace steel frame. Then base shear and layer displacement angle of the two structure areanalyzed and compared. The results show that buckling-restrained brace can dissipatemuch more seismic energy under severe earthquake and reduce base shear and layer displacement effectively.Finally, Pushover analysis of buckling-restrained brace steel frame is carried outand gets points of performance under frequently occurred earthquake and severeearthquake. The effect of buckling-restrained brace is the same as conventional brace’seffect, because it remains elastic behavior under frequent earthquake. Under the severeearthquake, buckling-restrained braces have obvious effect on hysteretic energydissipation, and increase the damp of structure and improve the seismic behavior ofsteel frame structure. Through check the states of plastic hinge on performance point ofsteel BRB-frame structure which is designed reasonably and the four steps before andone step after performance point, to find out that the structure can content withrequirements of code for seismic design of buildings.