A New Seismic Design Method for Steel Multi-Tiered Braced Frames

Abstract

A seismic design strategy is presented to design the columns of multi-tiered steel braced frames. Minimum strength and stiffness requirements are introduced for the columns under the seismic loads. The proposed method aims at reducing the concentration of ductility demand in one of the tiers and, thereby, the in-plane bending moment demand on the columns and the ductility demand on the bracing members. Nonlinear static and dynamic analyses are performed to validate the design procedure. Moreover, detailed finite element analysis is carried out to investigate the stability of the columns. The results show that the proposed design method can efficiently reduce the column in-plane flexural demand and the brace ductility demand.

Evaluation of AISC Seismic Design Methods for Steel Multi-Tiered Special Concentrically Braced Frames

“…Past numerical simulations showed that the seismic-induced demands in multi-tiered braced frames differ from those in standard multi-story concentrically braced frames, which, if not considered in the design, may result in column instability or excessive brace elongation that can lead to brace fracture (Imanpour and Tremblay, 2014;Imanpour et al, 2016a). The 2016 AISC Seismic Provisions have introduced design requirements for ordinary and special concentrically braced frames as well as buckling-restraint braced frames to prevent such unsatisfactory limit states in the braced frames with multi-tiered configurations.…”