Real-Time Hybrid Simulation of Shape Memory Alloy Dampers

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Increasing economical and technical requirements make the design of earthquake resistant civil engineering structures with traditional construction materials impossible. Shape memory alloys (SMA) are metallic smart materials with unique characteristics. Without any residual elongation, SMAs can recover their original shape after mechanical stress induced large deformations with even over 7 % strain. This so-called superelastic behaviour make SMA an attractive alternative to the existing damper systems, which show significant technical limitations. Conventional anti-seismic devices such as metallic steel dampers, which need to be replaced after each strong seismic excitation because of the non-recoverable plastic deformation, count as a representative example.A broader application of the SMA based dampers require further research both on the numerical and experimental part. Until now, researchers identified inconsistent and partly different results regarding the change process of the energy dissipation capacity of the SMAs. On the experimental part, full-scale shaking table tests with SMA damper are missing. On the numerical part, the existing constitutive models need to be improved. The studies revealed significant discrepancies regarding the seismic response of the SMA wires. The interaction of both the frequency effects and the strain amplitude together with the unique transient character of the earthquake loading are supposed to be the reasons for the inaccuracy of the existing models. In the proposed project, the seismic behaviour of SMA dampers using real-time hybrid simulations (RTHS) is analysed. Therefor the structure is partitioned into into physical and numerical substructures. RTHS provides a fullscale experimental solution by simulating controlled structures numerically while testing dampers experimentally.Furthermore, the research project aims to improve the existing constitutive models regarding the dynamic response of the SMA by differentiating between cyclic loading effects, meaning SMA behaviour under repeated loading conditions, and transient earthquake loading effects regarding the stochastic nature of seismic loading.