Computational study of self-centering buckling-restrained braced frame seismic performance Matthew R. Eatherton 1, * ,† , Larry A. Fahnestock 2 and David J. Miller 3 1 Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA, U.S.A. 2 Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, U.S.A. 3 Degenkolb Engineers, San Francisco, CA, U.S.A. SUMMARY Recent research developed and experimentally validated a self-centering buckling-restrained brace (SC-BRB) that employs a restoring mechanism created using concentric tubes held flush with pretensioned shape memory alloy rods, in conjunction with a buckling-restrained brace (BRB) that dissipates seismic energy. The present computational study investigated how the SC-BRB can be implemented in real buildings to improve seismic performance. First, a computational brace model was developed and calibrated against experimental data, including the definition of a new cyclic material model for superelastic NiTi shape memory alloy. A parametric study were then conducted to explore the design space for SC-BRBs. Finally, a set of prototype buildings was designed and computationally subjected to a suite of ground motions. The effect of the lateral resistance of gravity framing on self-centering was also examined. From the component study, the SC-BRB was found to dissipate sufficient energy even with large self- centering ratios (as large as 4) based on criteria found in the literature for limiting peak drifts. From the pro- totype building study, a SC-BRB self-centering ratio of 0.5 was capable of reliably limiting residual drifts to negligible values, which is consistent with a dynamic form of self-centering discussed in the literature. Because large self-centering ratios can create significant overstrength, the most efficient SC-BRB frame designs had a self-centering ratio in the range of 0.5–1.5. Ambient building resistance (e.g., gravity framing) was found to reduce peak drifts, but had a negligible effect on residual drifts. Copyright © 2014 John Wiley & Sons, Ltd. Received 14 October 2013; Revised 20 January 2014; Accepted 12 March 2014 KEY WORDS: steel braced frames; buckling-restrained braces; seismic effects; self-centering; shape memory alloy; response history analysis 1. INTRODUCTION Conventional seismic lateral force resisting systems (SFRS) such as moment resisting frames and braced steel frames are designed to undergo inelasticity during design level earthquakes (e.g., [1]). Historically, the focus in earthquake engineering has been to develop prescriptive requirements (i.e., design and detailing specifications) for these types of systems to produce sufficient inelastic deformation capacity so that the resulting structures do not collapse during an earthquake. Although the design approach is intended to focus inelasticity in ductile components, these components typically cannot be easily replaced. Furthermore, permanent lateral drifts that remain after an earthquake can occur as a result of inelasticity in the SFRS. Residual drifts and inelastic damage to nonreplaceable structural components can make it economically advantageous to demolish buildings after an earthquake rather than repair them. For example, studies have found that buildings with *Correspondence to: Matthew R. Eatherton, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061, U.S.A. † E-mail: meather@vt.edu Copyright © 2014 John Wiley & Sons, Ltd. EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. 2014; 43:1897–1914 Published online 14 April 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/eqe.2428