Cyclic testing and assessment of shape memory alloy recentering systems
Speicher, Matthew S.
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In an effort to mitigate damage caused by earthquakes to the built environment, civil engineers have been commissioned to research, design, and build increasingly robust and resilient structural systems. Innovative means to accomplish this task have emerged, such as integrating Shape Memory Alloys (SMAs) into structural systems. SMAs are a unique class of materials that have the ability to spontaneously recover strain of up to 8%. With proper placement in a structural system, SMAs can act as superelastic "structural fuses", absorbing large deformations, dissipating energy, and recentering the structure after a loading event. Though few applications have made it into practice, the potential for widespread use has never been better due to improvements in material behavior and reductions in cost. In this research, three different SMA-based structural applications are developed and tested. The first is a tension/compression damper that utilizes nickel-titanium (NiTi) Belleville washers. The second is a partially restrained beam-column connection utilizing NiTi bars. The third is an articulated quadrilateral bracing system utilizing NiTi wire bundles in parallel with c-shape dampers. Each system was uniquely designed to allow a structure to undergo large drift demands and dissipate energy while retaining strength and recentering ability. This exploratory work highlights the potential for SMA-based structural applications to enhance seismic structural performance and community resilience.