## 2 Literature Review
Although this testing procedure allows for a large number of tests to be performed within a limited amount of time and with reduced cost, the experimental results cannot be directly compared to those obtained from testing anchorsinstalled in masonry walls and conducted under unconfined conditions. Indeed, under unconfined conditions, the field of stresses around the tested anchor is not affected by the setup, and testing of anchors embedded in walls allows for the occurrence of all possible failure modes. Furthermore, the numerous parameters affecting the behavior in tension are investigated under more realistic conditions. In most of the aforementioned investigations, the experimental results are used to assess and calibrate equations aiming at predicting the resistance of injection anchors in tension. Thus, [PERSON] and [PERSON] [3] have compared their experimental results to resistances calculated based on the upper-bound theorem of the theory of plasticity. This comparison was found quite satisfactory. On the other hand, [PERSON] et al. [4] have proposed an empirical equation for the calculation of the pull-out capacity of anchors installed in unreinforced masonry. The comparison between calculated and experimental resistances (obtained from 230 tests compiled in a database) has shown that 93% of the calculated resistances were below the obtained test values, with an overall safety factor approximately equal to 2.29. On the contrary, [PERSON] and [PERSON] [16], assessed equations available in the literature against the database of experimental results on the pull-out resistance of injection anchors, performed by the authors and available in the literature. Their conclusion is that the examined equations are not suitable to safely calculate the tension resistance of injection anchors. [PERSON] et al. [7] have proposed an equation for the prediction of the tension strength of anchors by defining a stress model of the masonry solid surrounding the anchor. The evaluation of formulae of the literature by [PERSON] et al. [10] has proven the inadequacy of those formulae to predict the ultimate tension capacity of anchors in brick masonry, the predictions in some cases overestimating the anchor resistances. Finally, [PERSON] and [PERSON] [13] have assessed the equations included in the 2016 edition of TR 054 [1] and those included in the literature [17; 18]. The authors have confirmed that the available formulations fail to predict the tension resistance of the tested anchors. Moreover, cracking or damage to the wall are parameters that affect the anchor resistance but are not taken into account in the theoretical calculations. This brief survey of literature related to the behavior of injection and grouted anchors to masonry subjected to tension shows that (a) due to the importance of the subject, there is a significant corpus of experimental results. Several parameters, such as the diameter of the anchor, location in masonry, embedment length, and bonding material are examined, although not necessarily all of them in each of the experimental campaigns. Furthermore, (b) the results from testing anchors under repeated tension loading, although limited in number, clearly show the effect of this adverse loading condition on the behavior of anchors. This is an aspect that needs to be further investigated, in combination with parameters affecting the behavior of anchors in tension (e.g., location and embedment depth of the anchor to masonry, mechanical properties of the base materials, etc.). On the other hand, (c) the effect of cracks in masonry on the behavior of anchors is not systematically investigated. Nonetheless, the occurrence of cracks (either in the vicinity of an anchor or crossing it) is imminent at least in the case of moderate and strong earthquakes.