A PERFORMANCE-BASED SEISMIC DESIGN METHOD FOR ECCENTRICALLY BRACED STEEL FRAMES

The ideal failure mode of eccentrically braced steel frames is associated with the yield of interstory links and the formation of plastic hinges at the column base of the bottom story. Traditional design methods are based on the strength design theory and can hardly represent the inelastic behavior of structures. In this study, a performance-based seismic design (PBSD) method for eccentrically braced frames was proposed. The inelastic deformation was governed by the target drift and failure modes of structures. All links dissipated energy under excessive seismic loading, while other members remained elastic. That is, the interstory drift was uniform along the height of the steel frame, and no weak layers occurred for post-seismic recovery of the structure. The validity and credibility of the proposed method was demonstrated by ten-story K-shaped and Y-shaped braced frame buildings, applying pushover analysis and dynamic elastic-plastic analysis. Results show that the ultimate state of the designed frames approached the desired ideal failure mode. The inelastic deformation mainly occurred at interstory links. All links were involved in energy dissipation and no weak layers appeared. The proposed PBSD method is expected to offer engineering design reference for eccentrically braced steel frames.