Development and Evaluation of Seismic Retrofit Alternatives for Older Concentrically Braced Frames
Publication: Journal of Structural Engineering
Volume 143, Issue 5
Abstract
Concentrically braced frames (CBFs) have been used for seismic-lateral-force resisting systems for many years, but prior to approximately 1988, they were not designed to promote ductile response using capacity-based design. These older, nonductile CBFs (NCBFs) have been investigated in prior research that identified severe deficiencies in these systems, but some deficiencies had more detrimental consequences than others. This paper describes a research study to evaluate retrofit strategies for NCBFs. Welded and bolted continuous and split shear-plate connections, end-plate connections, split double-angle connections, and integrated gusset-shear plate connections were investigated. Retrofit strategies included brace replacement, concrete in-fill of a locally slender brace, weld overlay, bolt reinforcement, development of in-plane brace buckling, and the use of buckling-restrained braces. In all cases, system deformation capacity was enhanced, and the extent of improvement depended on connection configuration, connection demand-to-capacity ratios, and bracing type.
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Acknowledgments
This material is based on work supported by the National Science Foundation (NSF) Network for Earthquake Engineering Simulation under Grant No. CMMI-1208002 and the NSF Graduate Research Fellowship under Grant No. DGE-1256082. Independent financial support and material donations were provided by the American Institute of Steel Construction. In addition, the research team received advice from many practicing consultants. This advice and financial support is greatly appreciated. The tests were performed at the Structural Research Laboratory at the University of Washington, and the authors gratefully acknowledge the students and staff who conducted the tests. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring agencies.
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Published In
Journal of Structural Engineering
Volume 143 • Issue 5 • May 2017
Copyright
©2016 American Society of Civil Engineers.
History
Received: Jun 1, 2016
Accepted: Oct 28, 2016
Published online: Dec 8, 2016
Published in print: May 1, 2017
Discussion open until: May 8, 2017
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