Steel Structures Research Update: Strongback Steel-Braced Frames for Improved Seismic Behavior in Buildings

Abstract

While current AISC provisions have greatly improved the seismic behavior of conventional braced frame systems, they still have a tendency to form weak stories. The strongback system was developed as a method of delaying or preventing weak-story behavior. Conceptually, the inclusion of an “essentially elastic” backbone, or strongback, enforces a nearly uniform drift distribution, thereby engaging adjacent stories upon the initiation of inelastic behavior in the opposite braces. Ongoing work on the strongback braced frame is highlighted. The research is led by Dr. Stephen Mahin, professor at the University of California–Berkeley, and Byron L. and Elvira E. Nishkian, professors of structural engineering. Dr. Mahin currently leads the SimCenter as part of the Natural Hazards Engineering Research Infrastructure (NHERI) and was recently awarded an AISC grant to research and develop a possible design method for the strongback system.