Reducing Damage Concentration with a Strongback System: SEMM Seminar with Dual Presentations
Seminar | November 27 | 12-1 p.m. | 502 Davis Hall
Barbara Simpson, Department of Civil & Environmental Engineering, UC Berkeley
Multi-story braced frames exhibit large variations in inelastic demand over the building height and tend to concentrate damage in a few weak stories during an earthquake. This presentation will present the numerical and experimental results of a strongback system, a modification of the conventional braced frame that utilizes a vertical steel truss or spine to delay or prevent weak-story behavior. A cyclic test was performed on a nearly full-scale two story strongback retrofit design. The design was composed of two halves: an inelastic truss utilizing a buckling-restrained brace (BRB) to dissipate energy and an elastic truss designed to engage both stories to mitigate weak-story behavior. The strongback specimen was effective in impeding the formation of a weak-story mechanism and in mobilizing the reserve strength of other structural components, even after rupture of the BRB core. Test results established that the strongback can be a viable method of mitigating weak-story behavior, and subsequent numerical studies have shown that the strongback may also yield better performance than conventional braced frames. Ongoing numerical efforts have focused developing a reasonable design methodology to effectively utilize the strongbacks potential for increased seismic performance.