Comparative Study On Seismic Design Of Eccentrically Braced Steel Frames Between Chinese And American Codes

Recently,eccentrically braced steel frames have been widely used on high seismic zone both in China and America.Considering the advancement of American codes,comparison of seismic design method and seismic performances about eccentrically braced frames between China and America are studied in this paper,which is of great significance for further improve the Chinese seismic design codes for steel buildings.The main achievements of this study are as follows:(1)Basic requirements of Chinese and American seismic design codes such as seismic precautionary objective and criterion,seismic design method,site classification and seismic design force were compared.On basis of that,the coincidence relations of the site classifications and materials strength are determined between two codes,and the conversion relationships between the parameters of ground motions in Chinese and American codes are proposed.(2)Eccentrically braced steel frames of different height locating on Chinese 8-intensity(0.2g)region,designed following Chinese and American code systems on identical seismic hazard level,are selected as the research objects.The specific seismic design procedure of eccentrically braced frames in accordance with Chinese and American design codes respectively is illustrated,and the structural dynamic characteristics,base shear force,structural deformation,component dimensions and total amount of steel consumption were compared in detail.It is found that: as a result of the differences of seismic design between Chinese and American codes,the seismic design forces of the Chinese structure are relatively larger than that of the American structure.Besides,structural design method of eccentrically braced frame of Chinese codes is more conservative,so the amount of steel consumption of the Chinese structure is larger than that of the American structure.(3)The three-dimensional elasto-plastic analysis models of eccentrically braced frames designed following Chinese and American codes respectively were constructed in software Perform-3D.And static pushover analysis and dynamic nonlinear analysis have been carried out to evaluate their seismic performances.The results reveal that the yielding mechanism of components in the Chinese and American structures is consistent,yielding of components occur primarily in the links,which meets the expected design requirements,but the links in the American structures yield earlier.As a result of the variations in seismic design method between Chinese and American codes,the component dimensions of the eccentrically braced frame of the Chinese structures are larger than that of the American structures.So thedamage of the Chinese structures becomes lighter under the maximum considered earthquakes.Considering the Chinese structures and the American structures of different height exhibit roughly similar performances under earthquakes,all structures satisfy the respective seismic precautionary objectives.However,the total amount of steel consumption of the Chinese structures is larger,which is waste of material and money.