Experimental Evaluation of a Device Prototype Based on Shape Memory Alloys for the retrofit of historical buildings

Metallic tie rods are currently used in many historical buildings for absorbing the out-of-plane horizontal forces of arches, vaults and roof trusses, despite they exhibit several limitations under service and seismic conditions. In this paper, a post-tensioned system based on the superelastic properties of Ni-Ti Shape Memory Alloys (SMA) is proposed for improving the structural performances of traditional metallic tie rods. First, the thermal behavior under service conditions is investigated, based on the results of numerical and experimental studies. Subsequently, the seismic performances under strong earthquakes are verified trough a number of shaking table tests on a 1:4-scale timber roof truss model. The outcomes of these studies fully confirm the achievement of the design objectives of the proposed prototype device.