Shape Memory Alloys for Earthquake Building Protection

摘要

Use of Shape Memory Alloys (SMA) is more and more frequent in engineering because of their unique properties ofcompletely recovering the imposed deformations after heating, or automatically returning to the unloaded configurationvia a super-elastic process after very large strains (till around 10%). The process is regulated by a phase change in thematerial, shifting between martensite and austenite. Along this transformation, some SMA change their elastic propertiesby a factor three and damping coefficient by a magnitude. Super-elastic materials exhibit stable hysteresis loops undercyclic loading and dissipate energy without residual deformation thus providing in perspective self-centering capabilityfor use in buildings earthquake protection. The present study investigates the performance of SMA-based devices forseismic protection of reinforced concrete structures. In countries with high seismic hazard, vulnerability assessment ofexisting constructions and seismic retrofit implementation is a major challenge for both scientific community and publicadministration. This paper illustrates seismic retrofit of an existing school building in Italy, using dissipating steelbraces. Both SMA-wire dampers and mixed devices combining SMA elements and classical buckling-restrained axialdampers are considered for seismic upgrading. Adopted technique effectiveness and reliability are investigated bycomprehensive nonlinear static and dynamic analyses. Numerical results show that super-elastic SMA dampers areeffective for mitigating building response to strong earthquakes and providing systems self-centering capability withnegligible residual strains.