In this paper, a low-impact technique for the seismic strengthening of fair-face masonry walls is presented. The reinforcement solution involves the use of carbon-fibre reinforced polymer (CFRP) connectors installed from the outside by perforating the natural stone elements, combined with grout injections. The connectors cover ¾ of the thickness of the masonry, so as to leave the inner surface of the wall undisturbed. Once inserted, they are also substantially invisible from the outside.

The research was conducted as part of research programmes funded by Lazio Region after the 2016-2017 earthquakes in Central Italy, to support scientific and technological innovation in seismic protection, and by the National Civil Protection Department through the ReLUIS consortium. In this context, shake table tests were carried out on two full-scale specimens, one as built and the other strengthened, of irregular multi-leaf stone masonry walls to investigate the seismic performance of the proposed intervention solution. In order to replicate materials and construction technique of the Apennine buildings, the prototypes were made from stones recovered from the debris of a settlement in the municipality of Accumoli, while the mortar was designed to reproduce historical lime-poor practice.

The experimental setup was designed to induce out-of-plane vertical bending in the presence of seismic motion at the base, while allowing the vertical displacement of the wall. As seismic input, the horizontal and vertical components of three records belonging to the 2016-2017 seismic sequence were selected. The experimental activity carried out aims to contribute to the ongoing debate on the post-earthquake reconstruction and to propose a new technology for the seismic protection and for the preservation of historical buildings in the Apennines.