Design And Seismic Performance Of Tied Braced Steel Frames

The tied braced steel frames(TBFs)were developed to achieve uniform inelastic deformation in the eccentrically braced steel frames(EBFs)by connecting links across the entire frame height with tie members.The existing design method of the TBFs is complicated,and the design is slightly conservative for high-rise structures,the applicability of the method needs to be improved.In order to improve the design method of the TBFs and promote its application,the design method and seismic performance of the structure were studied in this paper.The specific work of this paper is as follows:(1)Based on the ideal failure mode of the TBFs,a novel design method was proposed,and the suggestion design equations of non-energy dissipation members such as the braces,columns and ties were given.The applicability of the method was verified by the elasticplastic analysis of a prototype structure.(2)In order to prove the advantages of the tied braced steel frame and the design method,the TBFs and traditional K-eccentrically braced frames(K-EBFs)were designed by different design methods.Which were compared the uniform degree of inter-story drift ratio,energy dissipation and internal force of the structures,was studied by analyzing the nonlinear time-history analysis.At the structural level,the link shear forces of the TBFs were transmitted through the ties,so that the links can work together owing to their deformation compatibility.The TBFs had more uniform distributions of the normalized inter-story drift ratios and link shear forces than those of the traditional K-EBFs,resulting in better damage distribution and more ductile behavior.At the design level,for the TBFs designed by the method of this paper,the section of the links was selected according to the story stiffness,so that the links can yield in each story,their plastic energy dissipation function can be fully played.And the tie axial force was also more reliable,the design value of the tie axial force was basically larger than the actual value.In addition,the cross-sections of the ties designed by the method of this paper were also less,which can reduce the amount of steel.(3)Incremental dynamic analysis and fragility analysis were carried out for the TBFs and K-EBFs.The seismic performance of the structures was evaluated by the exceedance probability of the damage state,vulnerability index,and collapse margin ratio.The results showed that the TBFs can reduce the occurrence of weak story,so that the exceedance probabilities of the extensive and collapse of the TBFs were less than the K-EBFs,their collapse-resistant performance were also better.When the ground motion intensity is large,the TBFs designed by the method of this paper exhibited better seismic performance due to their more uniform plastic energy dissipation of the links.