The behaviour of SMA isolation systems based on a full-scale release test

Two full-scale isolation re-centring devices, embodying NiTi Shape Memory Alloy elements, were designed and manufactured as the final product of a European research project for the exploitation of SMA's in the seismic protection of structures (MANSIDE Project). The devices were subjectod to several experimental tests aimed at verifying the feasibility and evaluating the mechanical properties of SMA-based devices for the passive seismic protection of buildings and bridges. In order to fully check the applicability of SMA-based isolation systems in real situations, the two devices were temporarily installed in a small base-isolated building, at Rapolla, Southern Italy, which was subjected to several in situ release tests. The complete SMA-based isolation system consisted of the SMA re-centring devices and steel-PTFE lubricated sliding bearings. The release tests were carried out by moving the superstructure and then suddenly releasing it. Numerical seismic simulation analyses have also been carried out to evaluate the effects of the variations of the mechanical characteristics of the isolation systems, including those due to temperature, on the seismic behaviour of the building. Based on these results, a proposal for the improvement of the performances of SMA based isolation systems is made and verified by numerical simulations