Higher-Mode Force Demands in Systems
Employing Elastic Strongback Spines

NHERI Lehigh Seminar Series
April 1, 2020 | 4pm-5pm EST


Research has identified the potential advantages of pivoting seismic force-resisting systems that employ an elastic spine, or “strongback”. The strongback is represented by a truss or stiff column that is designed to remain essentially elastic, thus providing a load path that can be used to transfer inelastic demands across all stories. As such, strongback systems are expected to result in more uniform drift distributions, reduced peak inelastic demands, and improved design flexibility compared to conventional seismic force-resisting systems. However, since the strongback is designed to remain elastic in every mode, systems employing strongback spines can exhibit near-elastic higher-mode force and acceleration demands. This higher-mode response is fundamentally different from systems which can form yield mechanisms in every mode, thereby limiting the accelerations that can develop in the first and higher modes. A series of investigations were aimed at understanding the dynamic response of strongback systems and developing static design methods to proportion the elastic members in the strongback spine.

About The Author

Dr. Barbara Simpson is an Assistant Professor of Civil and Construction Engineering at Oregon State University. She received her Ph.D. from UC Berkeley and her Bachelor of Science from the University of Kansas. She uses advanced computational and experimental methods to characterize structural response. Her aim is to develop innovative structural systems that improve building performance and reduce the effects of natural hazards on the built environment. Research areas include resilient design and retrofit of building structures, performance-based earthquake engineering, and next-generation computational modeling, optimization, and simulation, such as the development of hybrid simulation methods for wave-structure interaction.

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