A new numerical limit analysis-based strategy to retrofit masonry curved structures with frcm systems

In most historic masonry structures, curved geometries, such as arches or vaults, are key structural components to the overall building stability. Therefore, it is crucial to assess their safety level with respect to changes in the boundary conditions (increased loads or settlements). If the safety level of the structure needs to be enhanced, a strategy to intervene and retrofit structural members is represented by the use of Fabric Reinforced Cementitious Matrix (FRCM) systems. These types of externally bonded composite materials, made of high-strength textiles embedded in inorganic matrices, are proven to be a particularly advantageous strengthening solution for curved masonry structures. Even though limit analysis approaches such as Thrust Network Analysis (TNA) have been widely used to assess structural stability, their use in a retrofitting framework is seldom explored. This paper proposes an automated procedure to design the FRCM reinforcement required in masonry structures based on an initial TNA assessment analysis. To perform these analyses, a nonlinear programming problem is implemented and solved to compute the minimum reinforcement required for stability. These quantities are then used to design the FRCM reinforcement according to existing regulations. Finally, the load-bearing capacity of the reinforced structure can be re-evaluated for different load cases ensuring that the structure is safe. The effectiveness of the proposed approach is benchmarked against laboratory tests and demonstrated on arched structures.