Design criteria for strengthening of masonry vaults with Textile Reinforced Mortar

Textile Reinforced Mortar (TRM) also known as Fabric Reinforced Cementitious Matrix (FRCM) represents a valid alternative to Fiber Reinforced Polymers (FRP) for structural strengthening. The use of inorganic matrix in place of epoxy resin produces a substantial advantage in terms of physical and chemical compatibility with the substrate, especially for application to masonry members (walls or vaults). However, the increasing use of TRM systems for repair and strengthening of masonry structures is carried out in the absence of specific rules for design and assessment. Aiming at filling this lack in regulation, a joint committee between ACI 549 and RILEM TC250 was established. Based on the experimental results and modelling approaches available in the literature, a preliminary database of the significant parameters characterizing the mechanical behaviour of TRM/FRCM systems applied to masonry vaults was collected. More precisely, the load and displacement capacity of masonry vaults strengthened with FRCM composites are put in relationship with the mechanical parameters characterizing the tensile and bond properties of the strengthening systems. In such a framework, the following relevant aspects are considered: i) the contribution of the strengthening system in terms of additional capacity of the vault with respect of the delamination phenomenon; ii) the influence of the curvature on the capacity of the reinforcement and on its bond to the substrate; iii) the comprehensive effect on the overall deformability of the strengthened structure. Based on the collected data, an analytical approach is proposed to draw up simplified design rules that can be used for application to real cases.