Strengthening interventions based on grouted anchors made of fibre reinforced plastic (FRP) materials have recently gained a growing interest in improving the out-of-plane (OOP) response of masonry walls. Indeed, the durability of such a typology of anchors and their low weight-to-strength ratio are relevant features for preferring these materials to more traditional ones. However, despite the availability of experimental investigations about the bond performance of different types of grouted anchors, assessing their contribution to the OOP response of masonry walls is still a matter of ongoing research.

This paper presents the results of several limit analyses carried out by means of an improved macro-block modelling approach with frictional resistances. Adopting the kinematic method of limit analysis, the minimum load multiplier and the geometry of the failure mechanism are directly provided for each unreinforced and strengthened masonry system. The first improvement introduced in this paper concerns a better characterization of the geometry of the failure mechanism, since the variability of both the vertical position of the hinge and the crack inclination angle is introduced. Another improvement is the simplified assessment of the contribution of the anchors to the stabilizing moment, which allows to provide a simpler calculation in favour of safety. Moreover, the effects on the load multiplier and on the failure mechanism of some parameters regarding the masonry walls and the strengthening system are considered.