Design formulas for FRCM strengthened masonry elements under compression or shear load

The increasing interest in the field of conservation of existing masonry structures pushed to the development of new retrofitting technologies in the recent past. One of the most promising is the use of Fabric Reinforced Cementitious Mortar (FRCM), which consists of an open-grid within an inorganic matrix. The effectiveness of the FRCM-application is well-demonstrated in literature by several experimental investigations regarding different structural members, including columns and shear wall. The success of FRCMs is manly related to durability aspects, since the grid is generally non-metallic, the compatibility of the inorganic matrix with the substrates, the easy application, the low weight and spatial impact, the possible installation in damp areas and at high temperatures. The interaction between the substrate, the mortar-based matrix and the open-grid make challenging the theoretical prediction of the mechanical behavior of the FRCM-retrofitted structures. For this reason, the analytical formulations for the proper design of FRCM-strengthening are still an open research problem, referring to both short and long term conditions. The present paper reports and discusses design-oriented relationships for FRCM-confinement and in-plane FRCM-strengthening of masonry elements; the proposals are intended to satisfy the requirements of simplicity and accuracy needed for code-finality.