The use of FRP materials as external reinforcement of masonry structures has been recognized as an effective and minimally invasive method ofwall strengthening. The available literature and research reports confirmthe positive effect of the strip-like arrangement of composites with a horizontal, diagonal and – as shown in the paper – vertical configuration. The problem here is the proper estimation of the benefits of such FRP reinforcement, namely determining the real increase in shear strength. The paper described selected calculation procedures that can be found in the available literature (proprietary solutions), as well as in the published guidelines for the design of masonry walls strengthening using FRP materials. The results of experimental tests of sheared masonry walls made of AAC blocks and strengthened using vertical strips of carbon and glass fibres are briefly presented. Finally, based on the presented formulae, the values of the theoretical shear force resulted from the FRP contribution were calculated and detailed discussed.
The comparison of the experimental and theoretical shear forces showed that only one of the presented calculation methods gave a high agreement of the results for both carbon and glass sheets. In addition, it was noticed that in two cases the effects of strengthening – depending on the material used – drastically differed, which was not observed in the research.

The selection of the most proper strengthening method/system with an assessment of its effectiveness is quite complicated in the case of masonry structures, mainly due to their huge diversity in materials. The most popular strengthening materials based on the composite fibres and are laid on the masonry wall using epoxy adhesives (FRP system) or mineral mortars (FRCM system). This article presents a comparison of external strengthening made using different glass-fibre-based materials on the behaviour of specific masonry walls. The walls are made of AAC blocks (Autoclaved Aerated Concrete), commonly used in rather low urban buildings or skeleton construction. As a strengthening material the GFRP sheets and two types of glass meshes are used. The walls are subjected to diagonal compression, which reflects the shearing of the walls. The scope of research describes cracking stage, shear capacity and analysis of the mode of failure of tested walls.