Low-impact techniques for seismic strengthening fair faced masonry walls

Two techniques for the seismic strengthening of fair faced rubble masonry walls are proposed and tested on a shake table. The first solution entails the use of carbon fibre reinforced polymer connectors installed from outside through the natural stone units, without perforating the entire wall thickness, thus leaving the internal wall surface undisturbed. In the second solution, stainless-steel cords are embedded in repointed mortar joints of the fair face and connected, by means of stainless-steel bars, to a thermo-insulating composite reinforced mortar applied to the internal side. Shake table tests were performed under natural accelerograms on real scale multi-leaf rubble masonry walls, built with the stone units retrieved from the debris of a hamlet heavily damaged in the 2016 Central Italy earthquakes. Both strengthening solutions proved effective in enhancing the seismic capacity by preventing leaf separation and masonry disintegration, and in limiting damage development under earthquake excitation. Thanks to the compatibility with original materials and the preservation of the fair face, they are suitable for mitigating the seismic vulnerability of architectural heritage.