AN INNOVATIVE ISOLATION BEARING WITH SHAPE MEMORY ALLOYS

This paper presents a new isolation device concept using shape memory alloy elements, to evaluate the possibility of its application and to investigate the effectiveness in reaching the structural design goals compared with traditional isolation devices. Shape memory alloys (SMAs) are characterized by unique mechanical properties due to solid-solid transformation between phases of the alloy. The nonlinear hysteresis due to the superelastic effect, which can be described by a flag shape relation, provides supplemental damping, reduction on the residual deformation given by the recover of the original shape, and limitation on the force transmitted to the connected elements. Moreover it is possible to obtain high strength and strain capacity, high resistance to corrosion and to fatigue. Actual devices used in base isolated systems have been taken into account and “equivalent ” SMA isolation devices have been designed to get the same characteristics in term of global structure period elongation, displacement capacity, capability to sustain the base shear and the vertical load, but also in order to provide energy dissipation and to sensibly reduce residual deformations. The design device process has been then checked through numerical analyses comparing the response of SMA bearing systems and “traditional ” bearing systems and their effectiveness on the global structural response