Experimental study of CRM-reinforced brick masonry panels: Cyclic shear-compression tests and compression tests

The preservation of the building heritage is often accompanied by the necessity of ensuring adequate structural safety of existing buildings. Existing masonry structures are usually characterised by a high seismic vulnerability due to their low tensile strength; moreover, despite the significant compressive capacity, often masonry panels are not able to guarantee the safety level required by the current building codes under gravitational loads, due to their slenderness and the possible out-of-plane actions. In recent years, several systems have been developed for the reinforcement of masonry buildings based on the use of composite materials externally bonded to the structural elements. Among them, the CRM system can be used for the static and seismic reinforcement of masonry piers as an alternative to the traditional reinforced plaster. The CRM system consists of the application on the panel surfaces of a mortar layer about 3 cm thick reinforced with a glass fibre grid and connected to the wall through transversal connectors. Despite its increasing use, to date, few experimental and theoretical studies have been carried out focusing on the lateral behaviour of reinforced panels, especially regarding their flexural response and drift capacity, as well as a little number of studies are available regarding the contribution provided by CRM layers on the buckling failure of panels induced by vertical loads. This work presents an experimental campaign carried out at the Laboratory of Structures and Materials of the University of Florence. A series of tests for the mechanical characterisation of materials composing the masonry and the reinforcement has been at first performed; then, quasi-static cyclic shear-compression tests and compression tests on solid brick masonry panels strengthened with CRM have been performed, considering the application of the CRM on a single or both faces of the walls. Tests allowed the assessment of the mechanical properties of the retrofitting system and its adhesion to the substrate and highlighted the advantages and limitations produced in the structural response of reinforced walls, both for horizontal and vertical loading.