Seismic energy and axial column demands of steel concentrically braced frames

Abstract

Steel concentrically braced frames are widely used in seismic regions. Current engineering practices advocate the utilization of concentrically braced frames with elastic beams. Nevertheless, there is a noticeable dearth of comprehensive studies and recommendations regarding the seismic energy demands and axial column demands of these frames, considering the influence of varying beam strength and stiffness. To comprehensively investigate seismic energy demands and axial column demands, this study involves the design of nine concentrically braced frames characterized by different heights (3-, 9-, and 18-story) and beam strength levels (including cases of serious yielding, medium yielding, and elastic beams) for dynamic analysis. The assessment of energy demands in key structural members and axial column demands of concentrically braced frames is conducted based on the dynamic analysis outcomes. In concentrically braced frames with yielding beams, there is a noticeable reduction in the energy demands among braces, whereas the energy demands within beams experience an increase. Furthermore, it is observed that the axial column demands in concentrically braced frames featuring yielding beams are more closely associated with the overstrength of the beams rather than conforming to the full plastic mechanism as suggested by AISC 341.