## 1 Introduction  
Many historical structures built with brick masonry show signs of structural degradation and damage caused by factors such as the action of environmental loads, lack of maintenance, or the occurrence of extreme events, e.g., fires or earthquakes [1, 2, 3]. In numerous occasions, these buildings have lost their horizontal structural elements, remaining only with their walls. Moreover, it is common practice to preserve the masonry facades of historical buildings due to their architectural value. In order to prevent these vertical cantilevers from collapsing, temporary or permanent shoring, as well as structural stabilization through the incorporation of new structural elements are usually adopted. The connection between the old masonry walls and the new structural elements can be achieved in different ways and using various materials. A commonly accepted choice involves the application of metal anchors or fasteners. It is noted that the use of anchoring,often with external elements, is especially suited for repair and strengthening of historical structures as it allows minimal interventions with moderate aesthetic impact [4]. Similarly, the application of anchors is equally appropriate for contemporary structures. There are two main types of anchoring systems, namely, adhesive anchors and mechanical anchors, each type with its own subcategories. Adhesive or bonded systems can be further subdivided into chemical and grout anchors. The former type uses resin to create the bond with the substrate material, whereas grouting systems employ inorganic binders. Both systems are mostly applied through injection. Chemical anchoring usually consists of two adhesive components that are mixed during application. On the other hand, cement-based mixtures are commonly used for grout anchors. Both systems require a curing period to harden and gain strength. The curing period is shorter in the case of resins; therefore, chemical anchors are most used when a quick setting is needed. Moreover, chemical anchors require smaller drill holes, 10% to 25% larger than the diameter of the fastener, whereas grout anchors need drill holes 50% to 100% larger than the fastener diameter [5]. Mechanical anchoring is based on direct contact between the anchor and the substrate, with the corresponding transfer of loads through friction. Among the mechanical fasteners, the most common types are expansion and undercut anchors. The former type expands during installation and comprises two subcategories, namely, torque-controlled and deformation-controlled. For the torque-controlled anchors, tightening the bolt or nut activates the expansion mechanism. Alternatively, for deformation-controlled anchors, the expansion is caused by the displacement of an expander plug within a sleeve. In turn, undercut anchors establish a mechanical interlock with the substrate by means of a larger cavity at the end of the drill hole. According to the Guidance Note by the Construction Fixings Associations [6], the types of anchoring systems recommended for solid brick masonry are adhesive as well as torque-controlled expansion anchors. These guidelines provide additional considerations for the installation of the different types of anchors with the purpose of improving the quality of the connection: drilling the holes according to the specified depths and diameters; ensuring the cleanliness of the drill holes; verifying that the anchors are centrally placed within the drill hole; and ensuring the correct preparation of the adhesives, e.g., water/binder ratio for cementitious grout considering the water absorption capacity of the substrate material; among others [4; 6; 7]. The connection between the substrate material and the anchors deserves special attention, since it constitutes a key component of the overall structural response. In this context, a number of experimental works have been carried out to characterize the pull-out resistance of metal anchors, e.g., [7; 8; 9; 10; 11].