In-plane behaviour of FRCM-strengthened masonry panels

The evolution of seismic design regulations together with the degradation of the monumental heritage made necessary to increase the structural safety of a large variety of masonry buildings. A recent strengthening technique consists in the application of a fiber grid/unidirectional sheet with lime or cementitious mortar (FRCM), thanks to several advantages of this retrofitting system in comparison to traditional epoxy-based materials (FRPs), such as better compatibility with the masonry substrate, resistance to high temperatures and reversibility. In this paper, the results of in-plane tests performed on panels strengthened with different types of FRCM systems (that differ in layout, matrix, grid materials and spacing) are presented, after a complete mechanical characterization of FRCM materials, carried out through direct tensile tests and single-lap shear tests. In diagonal compression tests (DCT), failure modes and global behavior of the panels were also analyzed using Digital Image Correlation (DIC) technique, for a better understanding of their in-plane behaviour.