Recent seismic events demonstrated that the high vulnerability of existing masonry buildings is often related to the out-of-plane failure of perimetral walls. Lack of a proper connection with adjacent walls or slabs may favorite a premature overturing failure (first mode) significantly compromising the performance of the entire building. Nowadays, several strengthening techniques are available on the market and they are effective in increasing the connection with adjacent walls. The use of mechanical anchors made with classic (steel) or innovative (composite) materials is an effective and widely used technique. They can be often installed operating from the exterior of the building, thus reducing the disruption of the intervention and the downtime related to installation process. Although many experimental and analytical studies demonstrating the effectiveness of the injected anchors are available in literature, several aspects still need to be investigated.

This research paper deals with the experimental response of injected steel anchors extracted from a full-scale tuff-masonry wall. The wall was fabricated in a laboratory environment and six anchors were extracted varying the diameter of the bar, the location (center or side of the wall) and the axial pressure.

A direct comparison of the results and of the observed failure mode is reported. The main outcomes and the variability of the strength of the anchors with the main studied variables are discussed.