Effect of column stiffness on braced frame seismic behavior

Gregory A. MacRae, Yoshihiro Kimura, Charles Roeder

Research output: Contribution to journalArticlepeer-review

232 Citations (Scopus)


Steel concentrically braced frames are generally designed to resist lateral force by means of truss action. Design considerations for columns in these frames are therefore governed by the column axial force while column bending moment demands are generally ignored. However, if the columns cannot carry moments, then dynamic inelastic time-history analyses show that a soft-story mechanism is likely to occur causing large concentrated deformations in only one story. Such large concentrations of damage are not generally seen in real frames since columns are generally continuous and they possess some flexural stiffness and strength. This paper develops relationships for column stiffness and drift concentration within a frame based on pushover and dynamic analyses. It is shown that continuous seismic and gravity columns in a structure significantly decrease the possibility of large drift concentrations. An assessment method and example to determine the required column stiffness necessary to limit the concentration of story drift is provided.

Original languageEnglish
Pages (from-to)381-391
Number of pages11
JournalJournal of Structural Engineering
Issue number3
Publication statusPublished - 2004 Mar


  • Bracing
  • Columns
  • Earthquake engineering
  • Framed structures
  • Seismic design
  • Seismic stability


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