Design, manufacturing, and testing of a hybrid self‐centering brace for seismic resilience of buildings

Abstract

AbstractThis study explores the development of a shape memory alloy (SMA)‐based hybrid self‐centering brace that combines NiTi superelastic cables with viscoelastic dampers. First, the behavior of individual components of the hybrid self‐centering brace, that is, SMA cables and viscoelastic damper is characterized under various experimental conditions. Then, three prototype hybrid self‐centering braces with a maximum force capacity of 172 kN are designed and fabricated. The experimental tests are conducted to reveal the response of the hybrid self‐centering braces under increasing loading displacement amplitude. The effect of loading rate and training loading cycles on the mechanical response of the braces are also analyzed. Furthermore, the low‐cycle fatigue behavior of the hybrid self‐centering braces is evaluated by testing two of the braces for up to 30 loading cycles at a relatively large displacement amplitude. For each experimental condition, the variation of certain mechanical properties such as equivalent stiffness and equivalent viscous damping are evaluated and analyzed. Three case‐study frames with various bracing systems (i.e., SMA brace, viscoelastic brace, and hybrid self‐centering brace) are designed and modeled in OpenSees. Nonlinear dynamic analyses are carried out under 44 far‐field ground motion records to illustrate the advantages of hybrid self‐centering brace on structural seismic performance. The results indicate that the developed SMA‐based hybrid self‐centering braces provide an average of 9% equivalent viscous damping at different loading amplitudes with a complete self‐centering characteristic. The response of the bracing system is not affected considerably by loading rate, but it is found to be sensitive to cyclic loading. The steel frame with hybrid self‐centering braces is capable of leveraging the benefits of self‐centering ability and energy dissipation capacity.