A novel hybrid strong-back system to improve the seismic performance of steel braced frames

Abstract

Soft-storey behavior is prevalent in steel braced frames designed and built following either current or pre-modern seismic standards. Based on past research, various rehabilitation or construction techniques have been proposed to detect underlying behavior patterns, increase ductility, reduce inter-storey drift, and achieve higher levels of performance in these frames. This paper investigates and presents numerical results for a newly introduced hybrid seismic resisting configuration using nonlinear cyclic and nonlinear time history analysis. This hybrid mechanism utilized a strong-back truss with shear links instead of the usual buckling braces in order to act as structural fuses. The strong-back part of this system utilizes a truss with strong braces that span the structure's height vertically to delay or eliminate soft-storey behavior and mobilizes all the shear links throughout the building's height. For this research, three different steel braced frames that use diverse bracing configurations were scrutinized, along with a typical strong-back system. Additionally, a new hybrid system that merges a strong-back with shear links at all levels was examined and compared to other systems. Results showed that this hybrid system can be a successful technique for preventing the soft-storey behavior. Moreover, the utilization of shear links as structural fuses in combination with strong-back frames has the potential to improve the seismic performance of conventional strong-back frames by engaging all of the links and utilizing the entire fuses' energy dissipation capacity.