Strongback System: A Way to Reduce Damage Concentration in Steel-Braced Frames

AbstractThis paper examines a newly developed seismic force-resisting system: the strongback system (SBS). To achieve improved seismic performance, this system combines aspects of a traditional concentric braced frame with a mast to form a hybrid system. The mast acts like a strong back to help resist the tendency of concentric braced frames to concentrate damage in one or a few stories during severe seismic excitations. The purpose of the strongback system is to promote uniform story drifts over the height of a structure. Three SBS prototypes were designed and analyzed considering a variety of earthquake excitations. Computed responses are compared with responses for three other braced frame systems. Results of quasi-static inelastic analyses, both monotonic and cyclic, are presented to demonstrate differences in the fundamental hysteretic behavior of the braced frame systems considered. A series of nonlinear dynamic response history analyses were then performed to compare the global and local dynamic re...