Shape Memory Alloy Devices for the Structural Improvement of Masonry Heritage Structures

Abstract

The development of innovative techniques based on shape memory alloy devices (SMADs), for the purpose of seismic protection for cultural heritage structures, began in Italy within the framework of an European Commission-funded project and continued with further studies and applications. These devices exploit a special property of shape memory alloys: their superelasticity—the ability to recover very high deformation without residual strain, associated with a non-linear constitutive behavior, making it possible to keep the force constant in a wide range of displacements. Consequently, SMADs can be used as special ties capable of limiting the forces transmitted between the structural elements that they connect (e.g., a church facade and the roof), at the same time allowing small displacements. Compared with very rigid conventional steel ties, SMADs are able to reduce accelerations and forces, and thus increase the seismic capacity of the structure. This article provides a brief overview about the research and development that led to the world's first applications of SMADs for seismic protection, within the framework of the post-earthquake restoration of the upper basilica of St. Francis in Assisi, Italy.