Research On Seismic Performance Of The Heterogenic Braced Steel Frame With Reduced Columns At The Bottom

With the development of social economics and technology,more and more high-rise buildings and large-span architecture appear in cities,much innovation in architectural field also emerge.Unique architectural image usually accompany heterogenic structures.Thereinto,buildings with reduced columns at the bottom often bring some harmful factors about structural intensity,rigidity and torsion.Structure designers need adopt special ideas and plans to avoid.For structures with reduced columns at the bottom,this paper is based on a research center,in order to study which scheme can improve disadvantages and enhance seismic performance,so that provide some helps and references for similar structural design.In this paper,some anti-seismic theory are introduced,then choose braced frame system and use finite element software Midas Gen to establish model.After that,adopting concentrical brace scheme,eccentrical brace scheme and buckling-restrained brace scheme,and change the number of brace's layer,brace's location and length of link beam to examine structure's property,comparing advantages and disadvantages of different scheme.Using multimobal analysis and response spectra analysis to analyse structure's rigidity and torsion,analyzing the stress ratio.Using linear analyze and nolinear analyze to examine structure's energy dissipation and shock absorption.Pushover analysis are used to examine the formed order of the plastic hinges and to examine structure's weak spots.The above Analysis results show that:(1)Strcture's rigidity will be stronger with increasing the number of brace's layer,puting braces outside of frame can reduce the torsion of structure,and brace can reduce the stress ratio of column,so that it can enhance the economy.(2)Those in less earthquake areas or below 7 degree earthquake intensity areas and designer treat the difficulty of construction as secondary cause should adopt eccentrical brace scheme,increasing the length of link beam within limits can enhance the anti-seismic property,however,if designers treat the difficulty of construction as principal factor,adopting concentrical brace scheme.(3)Those in 8 and higher degree earthquake intensity areas can adopt modified buckling-restrained brace scheme:if designers use the link beam as the first defense to earthquake,adopting modified eccentrical brace scheme,if designers use braces as the first defense to earthquake,adopting modified concentrical brace scheme.Buckling-restrained brace can exhibits good hysteretic performance under major earthquake,it can absorb much energy,putting them near the transformation layer can make the brace play a big role.