Strongback Braced Frames for Damage Protection of Earthquake Resistant Buildings

The current building codes are prescriptive in nature and are based on building's safety. To allow the community to recover from a seismic event within an expected timeframe, recently, researchers proposed to consider recovery-based objectives rather than safety-based objectives. To fulfill this criteria, the Strongback Braced Frame (SBF) has the potential to mitigate the weak-storey response and exhibit fast recovery after earthquake events. However, the design of strongback system is not straightforward. Although researchers proposed a design methodology for low-rise and middle-rise SBF buildings, the applications are limited to the installation of strongback inside the concentrically braced frame. This configuration, where one half of braced frame is elastic and the other is designed to carry 100% of base shear, leads to large size braces. Conversely, installing the SB exterior to the primary system requires smaller brace sizes, which enhance the energy dissipation. The main objectives of this paper are: i) to investigate the nonlinear response of SBFs with exterior strongback, and ii) to analyze the nonlinear response of SBF buildings subjected to subduction and crustal ground motions.