Influence of mortar coating type on the shear resistance of a GFRP based strengthening technique for brick masonry walls

A strengthening technique for increasing both the in-plane and out-of-plane resistance of masonry walls based on the application on both sides of the wall of a mortar coating reinforced with glass fiberreinforced polymer (GFRP) meshes is herein considered. A recent experimental campaign evidenced the effectiveness of this technique both in terms of resistance and deformation capacity of masonry walls. The paper focuses on the in-plane behavior of reinforced masonry, collecting the results of diagonal compression tests performed on solid brick masonry specimens enhanced by considering 17 different types of mortar for the coating (tensile resistances ranging from 0.7 to 3 MPa, Young modulus from 6000 to 23000 MPa). These experimental results are useful to extend the validity of an analytical formulation proposed by the authors and to investigate on the behavior of the reinforced masonry when the coating mechanical characteristics vary considerably. It emerged that the effectiveness of the reinforcement decreases with the increase of the mortar resistance and that the assessment of the reinforced masonry resistance as sum of the resistances of the masonry and that of the reinforced coating in not always on the safe side but has to be corrected through a coefficient. Based on the experimental results, a characteristic curve at 5% fractile was provided for this coefficient in function of the tensile strength of the mortar; the curve is represented by a decreasing exponential function with an asymptotic value at 0.8.