Theoretical and experimental studies for the application of shape memory alloys in civil engineering

Shape Memory Alloys (SMAs) have great potential for the use in the field of civil engineering. The authors of this manuscript have been involved, from 1996, in several experimental and theoretical studies of the application of SMAs in civil engineering, for national and international research projects. This paper provides an overview of the main results achieved, consisting in the conceptual design, implementation and testing of three families of SMA-based devices, namely: (i) special braces for framed structures, (ii) seismic isolation devices for buildings and bridges and (iii) smart ties for arches and vaults. The main advantage of using SMA-based devices in the seismic protection of structures comes from the double-flag shape of their hysteresis loops, which implies three favourable features, i.e.: self-centring capability, good energy dissipation capability and high stiffness at small displacements. The main advantage of SMArt ties comes from the thermal behaviour of SMA superelastic wires, which is opposite to that of steel rod. This implies a strong reduction of the force changes caused by variations of air temperature.