## 6 Conclusions  
Metal anchors are commonly used for the stabilization of masonry structures, either as a temporary solution for sharing purposes or for strengthening interventions in historical buildings. Nonetheless, the mechanical behavior of the anchoring systems needs further investigation, both in the experimental field and in the theoretical aspects with the development of more consistent predictive models, especially for historical brick masonry. This paper presented the results of an experimental campaign to study the load capacity of three types of metal anchors, namely, mechanical, chemical, and cementitious great stafeners, applied on brick masonry walls built in a laboratory. The experimental works included mechanical characterization tests for constituent materials and masonry specimens, as well as pull-out tests. Moreover, two sets of pull-out tests were performed, namely, with the actuator pulling in the axial direction of the anchors (tensile loading) and with a 30\({}^{\circ}\) inclination, with respect to the horizontal plane (combined tensile and shear loading). Considering the results of the pull-out tests, the chemical anchors showed better performance, with an average ultimate load about 14% higher than that of the grout and 111% greater than the value obtained for mechanical anchors. Conversely, the mechanical fasteners showed the lowest capacity. An overall reduction in the tensile capacity of all the anchoring systems was observed when the shear component was introduced. Furthermore, different failure modes and loading capacities were obtained even within the same type of anchors, which emphasizes the heterogeneous nature of masonry. In general, the predictive analytical formulas were proven inadequate to estimate the ultimate loading capacity of metal anchors applied in brick masonry. In particular, the capacity predicted for mechanical anchors under tensile loading and for adhesive anchors under shear loading was overestimated, which supposes a safety issue. It was recalled that most of the predictive formulas available in the literature were originally developed for concrete. Further experimental and analytical studies are, therefore, necessary to develop specific predictive models for masonry. It must be noted that the conclusions drawn from the presented work are limited to the specific studied cases, namely, the constituent materials and bond arrangement used \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Type of Anchor** & \begin{tabular}{c} **Average** \\ \(N_{p}\)**(kN)** \\ \end{tabular} & \begin{tabular}{c} **Average** \\ \(N_{R}\)**(kN)** \\ \end{tabular} & \begin{tabular}{c} \(N_{p}\)/\(N_{R}\)** \\ \end{tabular} & \begin{tabular}{c} **Average** \\ \(V_{p}\)**(kN)** \\ \end{tabular} & \
\begin{tabular}{c} **Average** \\ \(V_{p}\)**(kN)** \\ \end{tabular} &
\begin{tabular}{c} \(V_{p}\)/\(V_{R}\)** \\ \end{tabular} \\ \hline Mechanical & 12.72 & 17.23 & 0.74 & - & - & - \\ Mechanical & 7.41 & 11.31 & 0.66 & 4.28 & 4.43 & 0.97 \\ Chemical & 25.06 & 25.62 & 0.98 & - & - & - \\ Chemical & 17.47 & 10.84 & 1.61 & 10.09 & 29.08 & 0.35 \\ Grout & 21.68 & 10.84 & 2.00 & - & - & - \\ Grout & 15.71 & 10.84 & 1.45 & 9.07 & 29.08 & 0.31 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Relationship between experimental values obtained from the pull-out tests and estimated values. for the walls, the curing conditions, and the age at which the tests were performed. The intrinsic heterogeneity of masonry as a substrate material requires further research and more experimental investigation is needed to establish a richer, more robust database. In particular, additional studies are suggested with a special focus on different types of connectors, anchor diameter and embedment length, wall material and dimensions, confinement stresses, and actuator position, among other aspects. Conceptualization, R.R., R.M. and P.B.L. ; methodology, R.R., R.M. and P.B.L. ; validation, R.M. ; formal analysis, R.R. ; investigation, R.M. ; resources, P.B.L. ; data curation, R.M.